Electrosurgical apparatus and methods for laparoscopy

ABSTRACT

Electrosurgical methods and apparatus for treating tissue at a target site of a patient. An electrosurgical instrument includes a shaft, having a shaft distal end and a shaft proximal end, and an electrode assembly disposed at the shaft distal end. The electrode assembly includes at least one active electrode disposed on an electrode support. The instrument is adapted for coupling to a high frequency power supply or electrosurgical generator. Each active electrode is adapted for removing tissue from a target site and/or for localized coagulation of the target tissue. In one embodiment, the instrument is adapted for laparoscopic procedures.

RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 10/365,759, filed Feb. 14, 2003, now U.S. Pat. No. 7,331,957, thecomplete disclosure of which is incorporated by reference. U.S.application Ser. No. 10/365,759 is a continuation-in-part of U.S. patentapplication Ser. No. 09/766,168 filed Jan. 19, 2001, now U.S. Pat. No.6,589,237 which claims priority from U.S. Provisional Patent ApplicationNo. 60/233,345 filed Sep. 18, 2000, and claims priority from U.S.Provisional Patent Application No. 60/210,567 filed Jun. 9, 2000. U.S.patent application Ser. No. 09/766,168, now U.S. Pat. No. 6,589,237filed Jan. 19, 2001, is a continuation-in-part of U.S. patentapplication Ser. No. 09/197,013, filed Nov. 20, 1998, now U.S. Pat. No.6,296,638 which is a continuation-in-part of U.S. patent applicationSer. No. 09/010,382, filed Jan. 21, 1998, now U.S. Pat. No. 6,190,381,which is a continuation-in-part of U.S. patent application Ser. No.08/990,374, filed on Dec. 15, 1997, now U.S. Pat. No. 6,109,268, whichis a continuation-in-part of U.S. patent application Ser. No.08/485,219, filed on Jun. 7, 1995, now U.S. Pat. No. 5,697,281, which isa continuation-in-part of U.S. patent application Ser. No. 08/446,767filed Jun. 2, 1995, now U.S. Pat. No. 5,697,909, which is U.S. nationalstage entry of International Application No. PCT/US94/05168 filed May10, 1994, which is a continuation-in-part of U.S. patent applicationSer. No. 08/059,681, filed on May 10, 1993, now abandoned, which is acontinuation-in part of U.S. patent application Ser. No. 07/958,977filed Oct. 9, 1992, now U.S. Pat. No. 5,366,443, which is acontinuation-in-part of U.S. patent application Ser. No. 07/817,575filed Jan. 7, 1992, now abandoned, the complete disclosures of which areincorporated herein by reference for all purposes.

The present invention is related to commonly assigned U.S. ProvisionalPatent Application No. 60/062,997 filed on Oct. 23, 1997, U.S. patentapplication Ser. No. 08/977,845 filed Nov. 25, 1997, now U.S. Pat. No.6,210,402, which is a continuation-in-part of U.S. patent applicationSer. No. 08/562,332 filed Nov. 22, 1995, now U.S. Pat. No. 6,024,733,the complete disclosures of which are incorporated herein by referencefor all purposes. The present invention is also related to U.S. patentapplication Ser. Nos. 09/109,219, 09/058,571, 08/874,173 and 09/002,315,filed on Jun. 30, 1998, Apr. 10, 1998, Jun. 13, 1997, and Jan. 2, 1998,respectively and U.S. patent application Ser. No. 09/054,323 filed onApr. 2, 1998, U.S. patent application Ser. No. 09/010,382 filed Jan. 21,1998, and U.S. patent application Ser. No. 09/032,375 filed Feb. 27,1998, U.S. patent application Ser. No. 08/942,580, filed on Oct. 2,1997, U.S. patent application Ser. No. 08/753,227 filed on Nov. 22,1996, and U.S. patent application Ser. No. 08/687,792 filed on Jul. 18,1996, the complete disclosures of which are incorporated herein byreference for all purposes. The present invention is also related tocommonly assigned U.S. patent application Ser. No. 08/562,331 filed Nov.22, 1995, now U.S. Pat. No. 5,683,366, the complete disclosure of whichis incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of electrosurgery,and more particularly to surgical devices and methods which employ highfrequency electrical energy to ablate, resect, coagulate, or otherwisemodify a target tissue. The present invention also relates to apparatusand methods for the controlled removal of tissue at a target site byelectrosurgical ablation (e.g., Coblation®), and for efficientlyaspirating resected tissue from the target site, wherein the depth towhich tissue is removed can be precisely controlled with minimal or nocollateral damage, and all ablation by-products are removed via anaspiration unit.

Conventional electrosurgical methods generally reduce patient bleedingassociated with tissue cutting operations and improve the surgeon'svisibility. These electrosurgical devices and procedures, however,suffer from a number of disadvantages. For example, monopolarelectrosurgery methods generally direct electric current along a definedpath from the exposed or active electrode through the patient's body tothe return electrode, which is externally attached to a suitablelocation on the patient's skin. In addition, since the defined paththrough the patient's body has a relatively high electrical impedance,large voltage differences must typically be applied between the activeand return electrodes to generate a current suitable for cutting orcoagulation of the target tissue. This current, however, mayinadvertently flow along localized pathways in the body having lessimpedance than the defined electrical path. This situation willsubstantially increase the current flowing through these paths, possiblycausing damage to or destroying tissue along and surrounding thispathway.

Bipolar electrosurgical devices have an inherent advantage overmonopolar devices because the return current path does not flow throughthe patient beyond the immediate site of application of the bipolarelectrodes. In bipolar devices, both the active and return electrode aretypically exposed so that they may both contact tissue, therebyproviding a return current path from the active to the return electrodethrough the tissue. One drawback with this configuration, however, isthat the return electrode may cause tissue desiccation or destruction atits contact point with the patient's tissue.

Another limitation of conventional bipolar and monopolar electrosurgerydevices is that they are not suitable for the precise removal (ablation)of tissue. For example, conventional electrosurgical cutting devicestypically operate by creating a voltage difference between the activeelectrode and the target tissue, causing an electrical arc to formacross the physical gap between the electrode and tissue. At the pointof contact of the electric arcs with tissue, rapid tissue heating occursdue to high current density between the electrode and tissue. This highcurrent density causes cellular fluids to rapidly vaporize into steam,thereby producing a “cutting effect” along the pathway of localizedtissue heating. The tissue is parted along the pathway of vaporizedcellular fluid, inducing undesirable collateral tissue damage in regionssurrounding the target tissue site.

In addition, conventional electrosurgical methods are generallyineffective for ablating certain types of tissue, and in certain typesof environments within the body. For example, loose or elasticconnective tissue, such as the synovial tissue in joints, is extremelydifficult (if not impossible) to remove with conventionalelectrosurgical instruments because the flexible tissue tends to moveaway from the instrument when it is brought against this tissue. Sinceconventional techniques rely mainly on conducting current through thetissue, they are not effective when the instrument cannot be broughtadjacent to or in contact with the elastic tissue for a long enoughperiod of time to energize the electrode and conduct current through thetissue.

The use of electrosurgical procedures (both monopolar and bipolar) inelectrically conductive environments can be further problematic. Forexample, many arthroscopic procedures require flushing of the region tobe treated with isotonic saline, both to maintain an isotonicenvironment and to keep the field of view clear. However, the presenceof saline, which is a highly conductive electrolyte, can cause shortingof the active electrode(s) in conventional monopolar and bipolarelectrosurgery. Such shorting causes unnecessary heating in thetreatment environment and can further cause non-specific tissuedestruction.

Conventional electrosurgical cutting or resecting devices also tend toleave the operating field cluttered with tissue fragments that have beenremoved or resected from the target tissue. These tissue fragments makevisualization of the surgical site extremely difficult. Removing thesetissue fragments can also be problematic. Similar to synovial tissue, itis difficult to maintain contact with tissue fragments long enough toablate the tissue fragments in situ with conventional devices. To solvethis problem, the surgical site is periodically or continuouslyaspirated during the procedure. However, the tissue fragments often clogthe aspiration lumen of the suction instrument, forcing the surgeon toremove the instrument to clear the aspiration lumen or to introduceanother suction instrument, which increases the length and complexity ofthe procedure.

Endometriosis is a common condition due to the presence of ectopicendometrial tissue, usually within the abdominal cavity, which can leadto infertility in women. Endometrial lesions or implants respond toovarian hormonal changes, similar to the uterine endometrium. Symptomsof endometriosis include localized bleeding, pain, inflammation,scarring, and adhesion formation.

There is a need for improved treatment of endometriosis. Medical therapyfor endometriosis is basically hormonal. Treatment with continuousprogesterone can shrink endometriotic implants. Treatment that causes asignificant decrease in estrogen levels (pseudomenopausal state) isgenerally more effective than a prolonged progesterone effect. Agentsthat suppress ovarian estrogen production include Danazol (a weakandrogenic hormone), and Lupron (a gonadotropin-releasing hormoneagonist). Prescription of such products is usually limited to periods ofnot more than six months due to their side effects (including bonedemineralization and increased risk of cardiovascular disease). Often,the beneficial effects of such products are short-lived followingcessation of treatment. Prior to recent advances in laparoscopicinstrumentation and procedures, a common treatment for endometriosis waspelvic laparotomy. Lasers have been used for removal of endometriallesions. However, in the context of surgical ablation, lasers sufferfrom a number of disadvantages, as outlined hereinabove. Thus, there isa need for improved electrosurgical instruments which allow the removalof ectopic endometrial tissue from various sites during minimallyinvasive laparoscopic procedures, wherein the target tissue is removedin a highly controlled manner with little or no collateral damage.

The instant invention provides methods and electrosurgical apparatus forthe controlled removal or coagulation of target tissue duringlaparoscopic procedures with no or minimal damage to delicate, easilydamaged underlying tissue.

SUMMARY OF THE INVENTION

The present invention provides systems, apparatus, and methods forselectively applying electrical energy to structures or tissue of apatient's body. In particular, methods and apparatus are provided forresecting, cutting, ablating, aspirating, or otherwise removing tissuefrom a target site in situ, during laparoscopic procedures. Theinvention also provides systems and apparatus for spot coagulation andablation of target tissue, such as ectopic endometrial tissue present ondelicate underlying tissue or organs, such as the ovaries, ureter,urinary bladder, and bowel.

In one aspect, the present invention provides an electrosurgicalinstrument for treating tissue at a target site. The instrumentcomprises a shaft having a proximal portion and a distal end portion.One or more active loop electrodes are disposed at the distal end of theshaft. The loop electrodes preferably have one or more edges thatpromote high electric fields. A connector is disposed near the proximalend of the shaft for electrically coupling the active loop electrodes toa high frequency source.

The active loop electrodes typically have an exposed semicircular shapethat facilitates the removing or ablating of tissue at the target site.During the procedure, bodily fluid, non-ablated tissue fragments and/orair bubbles are aspirated from the target site to improve visualization.

At least one return electrode is preferably spaced from the activeelectrode(s) a sufficient distance to prevent arcing therebetween at thevoltages suitable for tissue removal and or heating, and to preventcontact of the return electrode(s) with the tissue. The current flowpath between the active and return electrodes may be generated byimmersing the target site within electrically conductive fluid (as istypical in arthroscopic procedures), or by directing an electricallyconductive fluid along a fluid path past the return electrode and to thetarget site (e.g., in open procedures). Alternatively, the electrodesmay be positioned within a viscous electrically conductive fluid, suchas a gel, at the target site, and submersing the active and returnelectrode(s) within the conductive gel. The electrically conductivefluid will be selected to have sufficient electrical conductivity toallow current to pass therethrough from the active to the returnelectrode(s), and such that the fluid ionizes into a plasma when subjectto sufficient electrical energy, as discussed below. In the exemplaryembodiment, the conductive fluid is isotonic saline, although otherfluids may be selected, as described in co-pending Provisional PatentApplication No. 60/098,122, filed Aug. 27, 1998, the complete disclosureof which is incorporated herein by reference.

In a specific embodiment, tissue ablation results from moleculardissociation or disintegration processes. Conventional electrosurgeryablates or cuts through tissue by rapidly heating the tissue untilcellular fluids explode, producing a cutting effect along the pathway oflocalized heating. The present invention volumetrically removes tissue,e.g., cartilage tissue, in a cool ablation process known as Coblation®,wherein thermal damage to surrounding tissue is minimized. During thisprocess, a high frequency voltage applied to the active electrode(s) issufficient to vaporize an electrically conductive fluid (e.g., gel orsaline) between the electrode(s) and the tissue. Within the vaporizedfluid, an ionized plasma is formed and charged particles (e.g.,electrons) cause the molecular breakdown or disintegration of tissuecomponents in contact with the plasma. This molecular dissociation isaccompanied by the volumetric removal of the tissue. This process can beprecisely controlled to effect the volumetric removal of tissue as thinas 10 to 50 microns with minimal heating of, or damage to, surroundingor underlying tissue structures. A more complete description of thisCoblation® phenomenon is described in commonly assigned U.S. Pat. No.5,683,366, the complete disclosure of which is incorporated herein byreference.

In variations of the invention which use Coblation® technology, the highfrequency voltage is sufficient to convert the electrically conductivefluid between the target tissue and active electrodes into an ionizedvapor layer or plasma. As a result of the applied voltage differencebetween active electrode(s) and the target tissue (i.e., the voltagegradient across the plasma layer), charged particles in the plasma(e.g., electrons) are accelerated towards the tissue. At sufficientlyhigh voltage differences, these charged particles gain sufficient energyto cause dissociation of the molecular bonds within tissue structures.This molecular dissociation is accompanied by the volumetric removal(i.e., ablative sublimation) of tissue and the production of lowmolecular weight gases, such as oxygen, nitrogen, carbon dioxide,hydrogen and methane. The short range of the accelerated chargedparticles within the tissue confines the molecular dissociation processto the surface layer to minimize damage and necrosis to the underlyingtissue.

During the process, the gases may be aspirated through opening 609and/or a suction tube to a vacuum source or collection reservoir. Inaddition, excess electrically conductive fluid and other fluids (e.g.,blood) will be aspirated from the target site to facilitate thesurgeon's view. Applicant has also found that tissue fragments are alsoaspirated through opening into suction lumen and tube during theprocedure. These tissue fragments are ablated or dissociated withelectrodes with a mechanism similar to that described above. Namely, aselectrically conductive fluid and tissue fragments are aspirated towardsloop electrodes, these electrodes are activated so that a high frequencyvoltage is applied to loop electrodes and return electrode (of course,the probe may include a different, separate return electrode for thispurpose). The voltage is sufficient to vaporize the fluid, and create aplasma layer between loop electrodes 540 and the tissue fragments sothat portions of the tissue fragments are ablated or removed. Thisreduces the volume of the tissue fragments as they pass through suctionlumen to minimize clogging of the lumen.

The present invention offers a number of advantages over conventionalelectrosurgery, microdebrider, shaver and laser techniques for removingsoft tissue in arthroscopic, sinus or other surgical procedures. Theability to precisely control the volumetric removal of tissue results ina field of tissue ablation or removal that is very defined, consistentand predictable. In one embodiment, the shallow depth of tissue heatingalso helps to minimize or completely eliminate damage to healthy tissuestructures, e.g., cartilage, bone and/or nerves that are often adjacentthe target tissue. In addition, small blood vessels at the target siteare simultaneously cauterized and sealed as the tissue is removed tocontinuously maintain hemostasis during the procedure. This increasesthe surgeon's field of view, and shortens the length of the procedure.Moreover, since the present invention allows for the use of electricallyconductive fluid (contrary to prior art bipolar and monopolarelectrosurgery techniques), isotonic saline may be used during theprocedure. Saline is the preferred medium for irrigation because it hasthe same concentration as the body's fluids and, therefore, is notabsorbed into the body as much as certain other fluids.

Systems according to the present invention generally include anelectrosurgical instrument having a shaft with proximal and distal endportions, one or more active electrode(s) at the distal end of the shaftand one or more return electrode(s). The system can further include ahigh frequency power supply for applying a high frequency voltagedifference between the active electrode(s) and the return electrode(s).The instrument typically includes an aspiration lumen within the shafthaving an opening positioned proximal of the active electrode(s) so asto draw excess or unwanted materials into the aspiration lumen undervacuum pressure.

In another aspect, the present invention provides an electrosurgicalprobe having a fluid delivery element for delivering electricallyconductive fluid to the active electrode(s) and the target site. In oneexemplary configuration, the fluid delivery element includes at leastone opening that is positioned around the active electrodes. Such aconfiguration provides an improved flow of electrically conductive fluidand promotes more aggressive generation of a plasma at the activeelectrode(s).

Alternatively, in some embodiments an electrically conductive fluid,such as a gel or liquid spray, e.g., saline, may be applied to thetissue using an ancillary device. In arthroscopic procedures, the targetsite will typically be immersed in a conductive irrigant, e.g., saline.In these embodiments, the apparatus may lack a fluid delivery element.In both embodiments, the electrically conductive fluid will preferablygenerate a current flow path between the active electrode(s) and thereturn electrode(s). In an exemplary embodiment, a return electrode islocated on the instrument and spaced a sufficient distance from theactive electrode(s) to substantially avoid or minimize current shortingtherebetween and to shield the tissue from the return electrode at thetarget site.

In another aspect, the present invention provides a method for applyingelectrical energy to a target site within or on a patient's body. Themethod comprises positioning one or more active electrodes into at leastclose proximity with the target site. An electrically conductive fluidis provided to the target site and a high frequency voltage is appliedbetween the active electrodes and a return electrode to generaterelatively high, localized electric field intensities at the surface ofthe active electrode(s). The active electrodes may be moved in relationto the targeted tissue to resect or ablate the tissue at the targetsite.

In another aspect, the present invention provides an electrosurgicalsuction apparatus adapted for coupling to a high frequency power supplyand for removing tissue from a target site to be treated. The apparatusincludes an aspiration channel terminating in a distal opening oraspiration port, and a plurality of active electrodes in the vicinity ofthe distal opening. The plurality of active electrodes may bestructurally similar or dissimilar.

In one embodiment, a plurality of active electrodes are arrangedsubstantially parallel to each other on an electrode support. In someembodiments, one or more of the plurality of active electrodes traversesa void in the electrode support. Typically, each of the plurality ofactive electrodes extends distally from a treatment surface of theelectrode support. According to another aspect of the invention, theplurality of active electrodes may be oriented in a plurality ofdifferent directions with respect to the treatment surface. In oneembodiment, a loop portion of each of the plurality of active electrodesis oriented in a different direction with respect to the treatmentsurface. In one embodiment, the orthogonal distance from the treatmentsurface to a distal face of each active electrode is substantially thesame.

According to one aspect of the invention, a baffle or screen is providedat the distal end of the apparatus. In one embodiment the baffle isrecessed within the void to impede the flow of solid material into theaspiration channel, and to trap the solid material in the vicinity of atleast one of the plurality of active electrodes, whereby the trappedmaterial may be readily digested.

In use, the plurality of active electrodes are coupled to a first poleof the high frequency power supply, and a return electrode is coupled toa second pole of the high frequency power supply for supplying highfrequency alternating current to the device. Each of the plurality ofactive electrodes is capable of ablating tissue via a controlledablation mechanism involving molecular dissociation of tissue componentsto yield low molecular weight ablation by-products. During this process,tissue fragments may be resected from the target site. Such resectedtissue fragments may be digested by one or more of the plurality ofactive electrodes via essentially the same cool ablation mechanism asdescribed above (i.e., involving molecular dissociation of tissuecomponents), to form smaller tissue fragments and/or low molecularweight ablation by-products. The smaller tissue fragments and lowmolecular weight ablation by-products, together with any other unwantedmaterials (e.g., bodily fluids, extraneous saline) may be aspirated fromthe target site via the aspiration channel.

In another aspect, the present invention provides a method for removingtissue from a target site via an electrosurgical suction device, whereina plurality of active electrodes are juxtaposed with the target tissue,and a high frequency voltage is applied to the plurality of activeelectrodes sufficient to ablate the tissue via localized moleculardissociation of tissue components. In one embodiment, the apparatus isadapted for efficiently ablating tissue and for rapidly removingunwanted materials, including resected tissue fragments, from the targetsite. In another aspect of the invention, the apparatus is adapted forproviding a relatively smooth, even contour to a treated tissue.

In another aspect, the present invention provides an electrosurgicalinstrument or probe adapted for coupling to a high frequency powersupply and for treating tissue at a target site. The instrument includesan electrode assembly including at least one active electrode disposedon an electrode support. In one embodiment, a plurality of activeelectrodes are arranged substantially parallel to each other on theelectrode support.

According to another aspect of the invention, an electrosurgicalinstrument includes an electrode support having a treatment surface anda recess within the treatment surface, and each of a plurality of activeelectrodes spans or traverses the recess. In one embodiment, each of theplurality of active electrodes includes a bridge portion spaced from thetreatment surface.

In another embodiment, an electrode support of an electrosurgicalinstrument includes a treatment surface and a recess within thetreatment surface, wherein the recess includes a void therein, the voiddefining an aspiration port adapted for aspirating unwanted or excessmaterials from a surgical site during a procedure.

In another aspect, the present invention provides an electrosurgicalinstrument including a shaft, and an electrode assembly disposed at adistal end of the shaft. In one embodiment, the shaft includes an innershaft and an outer shaft. According to one aspect of the invention, aproximal portion of the inner shaft lies within a distal portion of theouter shaft. In one embodiment, the inner shaft comprises a metal tubeor cylinder, while the outer shaft comprises an electrically insulatingtube.

According to another aspect of the invention, there is provided anelectrosurgical instrument including a shaft, having a shaft distal endand a shaft proximal end, and an integral fluid delivery element orunit. In one embodiment, the fluid delivery unit includes a plurality offluid channels, each fluid channel defined jointly by an external groovein the shaft distal end and an inner surface of a sleeve, wherein thesleeve ensheathes a distal portion of the shaft.

In another aspect, the invention provides a method of treating tissue ata target site using an electrosurgical instrument having at least oneactive electrode disposed on an electrode support. The activeelectrode(s) is/are positioned in at least close proximity to the targettissue, and a high frequency voltage is applied between the activeelectrode(s) and a return electrode, wherein the applied voltage iseffective in removing the target tissue in a controlled manner, suchthat underlying tissue exhibits little or no damage. According to oneaspect of the invention, the instrument and method are adapted forlaparoscopic procedures. In one embodiment, the method involves spotcoagulation and/or ablation of endometrial implants, and the instrumentis adapted for removing endometrial implants from delicate tissues ororgans, such as the bowel, ureter, and ovaries.

A further understanding of the nature and advantages of the inventionwill become apparent by reference to the remaining portions of thespecification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an electrosurgical system incorporatinga power supply and an electrosurgical probe for tissue ablation,resection, incision, contraction and for vessel hemostasis according tothe present invention;

FIG. 2 is a perspective view of another electrosurgical systemincorporating a power supply, an electrosurgical probe and a supply ofelectrically conductive fluid for delivering the fluid to the targetsite;

FIG. 3 is a side view of another electrosurgical probe according to thepresent invention incorporating aspiration electrodes for ablatingaspirated tissue fragments and/or tissue strands, such as synovialtissue;

FIG. 4 is an exploded view of a proximal portion of the electrosurgicalprobe;

FIG. 5 is a perspective view of another embodiment of the presentinvention;

FIG. 6 is a side-cross-sectional view of the electrosurgical probe ofFIG. 5;

FIG. 7 is an enlarged detailed cross-sectional view of the distal endportion of the probe of FIG. 5;

FIGS. 8 and 9 show the proximal end and the distal end, respectively, ofthe probe of FIG. 5;

FIG. 10 illustrates a method for removing fatty tissue from the abdomen,groin or thigh region of a patient according to the present invention;

FIG. 11 illustrates a method for removing fatty tissue in the head andneck region of a patient according to the present invention.

FIG. 12 shows an electrosurgical probe including a resection unit,according to another embodiment of the invention;

FIG. 13 shows a resection unit of an electrosurgical probe, theresection unit including a resection electrode on a resection electrodesupport;

FIGS. 14A-D each show an electrosurgical probe including a resectionunit, according to various embodiments of the invention;

FIG. 15A shows an electrosurgical probe including a resection unit andan aspiration device, according to the invention;

FIG. 15B shows an electrosurgical probe including a resection unit and afluid delivery device, according to one embodiment of the invention;

FIGS. 16A-F each show a resection unit having at least one resectionelectrode head arranged on a resection electrode support, according tovarious embodiments of the invention;

FIG. 17 illustrates an arrangement of a resection electrode head withrespect to the longitudinal axis of a resection unit;

FIG. 18A shows, in plan view, a resection electrode support disposed ona shaft distal end of an electrosurgical probe;

FIGS. 18B-D each show a profile of a resection electrode head on aresection electrode support;

FIGS. 19A-I each show a cross-section of a resection electrode head,according to one embodiment of the invention, as seen along the lines19A-I of FIG. 18B;

FIG. 20 schematically represents a surgical kit for resection andablation of tissue, according to another embodiment of the invention;

FIGS. 21A-B schematically represent a method of performing a resectionand ablation electrosurgical procedure, according to another embodimentof the invention;

FIG. 22 schematically represents a method of making a resection andablation electrosurgical probe, according to yet another embodiment ofthe invention;

FIGS. 23A and 23B show a side view and an end-view, respectively, of anelectrosurgical suction apparatus, according to another embodiment ofthe invention;

FIG. 23C shows a longitudinal cross-section of the apparatus of FIGS.23A, 23B;

FIG. 24A shows a longitudinal cross-section of the shaft distal end ofan electrosurgical suction apparatus, according to the invention;

FIG. 24B shows a transverse cross-sectional view of an active electrodeof the apparatus of FIG. 24A as taken along the lines 24B-24B;

FIG. 24C shows an active electrode in communication with an electrodelead;

FIG. 25A shows an electrosurgical suction apparatus having an outersheath, according to another embodiment of the invention;

FIG. 25B shows a transverse cross-section of the apparatus of FIG. 25A;

FIG. 26A shows a longitudinal cross-section of the shaft distal end ofan electrosurgical suction apparatus having a baffle, and FIG. 26B is anend view of the apparatus of FIG. 26A, according to another embodimentof the invention;

FIGS. 27A and 27B each show a longitudinal cross-section of the shaftdistal end of an electrosurgical suction apparatus, according to twodifferent embodiments of the invention;

FIGS. 28A and 28B show a perspective view and a side view, respectively,of the shaft distal end of an electrosurgical suction apparatus,according to another embodiment of the invention;

FIG. 29 is a block diagram schematically representing an electrosurgicalsystem, according to one embodiment of the invention;

FIG. 30 is a block diagram schematically representing an electrosurgicalinstrument including an electrode assembly, according to one aspect ofthe invention;

FIG. 31 is a block diagram schematically representing an activeelectrode for an electrosurgical instrument, according to anotherembodiment of the invention;

FIG. 32 schematically represents an electrosurgical instrument as seenin side view, according to another aspect of the invention;

FIGS. 33A and 33B are a side view and a cross-sectional view,respectively, of the distal end portion of an electrosurgical instrumenthaving a fluid delivery element, according to the invention;

FIG. 34A is a side view of an electrosurgical instrument, according toone embodiment of the invention;

FIG. 34B is a side view of the working or distal end of the instrumentof FIG. 34A;

FIG. 34C shows the working end of the instrument, as seen along thelines 34C-34C of FIG. 34B;

FIG. 34D shows a distal portion of the bridge portion of an activeelectrode as seen along the lines 34D-34D of FIG. 34C;

FIG. 34E is a perspective view of the working end of the instrument ofFIG. 34A, with the electrode(s) omitted for the sake of clarity;

FIG. 35 is a face view of an electrode assembly of an electrosurgicalinstrument illustrating the configuration of a plurality of activeelectrodes in relation to an electrode support, according to anotherembodiment of the invention;

FIG. 36 is a side view of a working or distal end of an electrosurgicalinstrument showing an active electrode protruding from a surface of anelectrode support, according to another embodiment of the invention;

FIG. 37 is a perspective view of an electrode support of anelectrosurgical instrument, showing a plurality of active electrodes ona treatment surface of the electrode support; and

FIG. 38 schematically represents a series of steps involved in a methodof treating a target tissue during a surgical procedure, according toanother embodiment of the invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The present invention provides systems and methods for selectivelyapplying electrical energy to a target location within or on a patient'sbody. The present invention is particularly useful in laparoscopicprocedures, such as procedures for the treatment of endometriosis, andin laparoscopic oncology. In addition, tissues which may be treated bythe system and method of the present invention include, but are notlimited to, prostate tissue and leiomyomas (fibroids) located within theuterus, gingival tissues and mucosal tissues located in the mouth,tumors, scar tissue, myocardial tissue, collagenous tissue within theeye or epidermal and dermal tissues on the surface of the skin. Otherprocedures for which the present invention may be used includearthroscopic procedures, laminectomy/diskectomy procedures for treatingherniated disks, decompressive laminectomy for stenosis in thelumbosacral and cervical spine, posterior lumbosacral and cervical spinefusions, treatment of scoliosis associated with vertebral disease,foraminotomies to remove the roof of the intervertebral foramina torelieve nerve root compression, as well as anterior cervical and lumbardiskectomies. The present invention is also useful for resecting tissuewithin accessible sites of the body that are suitable for electrode loopresection, such as the resection of prostate tissue, leiomyomas(fibroids) located within the uterus, and other diseased or abnormaltissue within the body.

The present invention may also be used to treat tissue or organs of thehead and neck, such as the ear, mouth, pharynx, larynx, esophagus, nasalcavity and sinuses. Such procedures may be performed through the mouthor nose using speculae or gags, or using endoscopic techniques, such asfunctional endoscopic sinus surgery (FESS). These procedures may includethe removal of swollen tissue, chronically-diseased inflamed andhypertrophic mucous linings, polyps and/or neoplasms from the variousanatomical sinuses of the skull, the turbinates and nasal passages, inthe tonsil, adenoid, epi-glottic and supra-glottic regions, salivaryglands, and other tissues; submucous resection of the nasal septum; andexcision of diseased tissue, and the like. In other procedures, thepresent invention may be useful for collagen shrinkage, ablation, and/orhemostasis in procedures for treating snoring and obstructive sleepapnea (e.g., soft palate, such as the uvula, or tongue/pharynxstiffening, and midline glossectomies); for gross tissue removal, suchas tonsillectomies, adenoidectomies, tracheal stenosis and vocal cordpolyps and lesions; or for the resection or ablation of facial tumors ortumors within the mouth and pharynx, such as glossectomies,laryngectomies, acoustic neuroma procedures; and nasal ablationprocedures. In addition, the present invention may also be used forprocedures within the ear, such as stapedotomies, tympanostomies, or thelike.

The present invention may also be useful for cosmetic and plasticsurgery procedures in the head and neck. For example, the presentinvention may be used for ablation and sculpting of cartilage tissue,such as the cartilage within the nose that is sculpted duringrhinoplasty procedures. The present invention may also be employed forskin tissue removal and/or collagen shrinkage in the epidermis or dermistissue in the head and neck, e.g., the removal of pigmentations,vascular lesions (e.g., leg veins), scars, tattoos, etc., and for othersurgical procedures on the skin, such as tissue rejuvenation, cosmeticeye procedures (blepharoplasties), wrinkle removal, tightening musclesfor facelifts or browlifts, hair removal and/or transplant procedures,etc.

For convenience, certain embodiments of the invention will be describedprimarily with respect to the treatment of endometrial implants;resection and/or ablation of the meniscus and the synovial tissue withina joint during an arthroscopic procedure; and to the ablation, resectionand/or aspiration of sinus tissue during an endoscopic sinus surgeryprocedure. However, it will be appreciated that the systems, apparatus,and methods of the invention may also be applied to procedures involvingother tissues or organs of the body, including open procedures,intravascular procedures, urological procedures, laparoscopy,arthroscopy, thoracoscopy or other cardiac procedures, dermatology,orthopedics, gynecology, otorhinolaryngology, spinal and neurologicprocedures, oncology, and the like.

In the present invention, high frequency (RF) electrical energy isapplied to one or more active electrodes in the presence of electricallyconductive fluid to remove and/or modify a target tissue or organ.Depending on the specific procedure, the present invention may be usedto: (1) volumetrically remove tissue, bone or cartilage (i.e., ablate oreffect molecular dissociation of the tissue structure); (2) cut orresect tissue; (3) shrink or contract collagen connective tissue; and/or(4) coagulate severed blood vessels.

In one aspect of the invention, systems and methods are provided for thevolumetric removal or ablation of tissue structures. In theseprocedures, a high frequency voltage difference is applied between oneor more active electrode(s) and one or more return electrode(s) todevelop high electric field intensities in the vicinity of the targettissue site. The high electric field intensities lead to electric fieldinduced molecular breakdown of target tissue through moleculardissociation (rather than thermal evaporation or carbonization).Applicant believes that the tissue structure is volumetrically removedthrough molecular disintegration of larger organic molecules intosmaller molecules and/or atoms, such as hydrogen, oxides of carbon,hydrocarbons and nitrogen compounds. This molecular disintegrationcompletely removes the tissue structure, as opposed to dehydrating thetissue material by the removal of liquid from within the cells of thetissue, as is typically the case with electrosurgical desiccation andvaporization.

The high electric field intensities may be generated by applying a highfrequency voltage that is sufficient to vaporize an electricallyconductive fluid over at least a portion of the active electrode(s) inthe region between the distal tip of the active electrode(s) and thetarget tissue. The electrically conductive fluid may be a gas or liquid,such as isotonic saline, delivered to the target site, or a viscousfluid, such as a gel, that is located at the target site. In the latterembodiment, the active electrode(s) are submersed in the electricallyconductive gel during the surgical procedure. Since the vapor layer orvaporized region has a relatively high electrical impedance, itminimizes the current flow into the electrically conductive fluid. Thisionization, under optimal conditions, induces the discharge of energeticelectrons and photons from the vapor layer to the surface of the targettissue. A more detailed description of this cold ablation phenomenon,termed Coblation®, can be found in commonly assigned U.S. Pat. No.5,683,366 the complete disclosure of which is incorporated herein byreference.

In one embodiment, the present invention applies high frequency (RF)electrical energy in an electrically conductive fluid environment toremove (i.e., resect, cut, or ablate) or contract a tissue structure,and to seal transected vessels within the region of the target tissue.The present invention may be used for sealing larger arterial vessels,e.g., on the order of 1 mm in diameter or greater. In some embodiments,a high frequency power supply is provided having an ablation mode,wherein a first voltage is applied to an active electrode sufficient toeffect molecular dissociation or disintegration of the tissue, and acoagulation (or sub-ablation) mode, wherein a second, lower voltage isapplied to an active electrode (either the same or a differentelectrode) sufficient to achieve hemostasis of severed vessels withinthe tissue. In other embodiments, an electrosurgical probe is providedhaving one or more coagulation electrode(s) configured for sealing asevered vessel, such as an arterial vessel, and one or more activeelectrodes configured for either contracting the collagen fibers withinthe tissue or removing (ablating) the tissue, e.g., by applyingsufficient energy to the tissue to effect molecular dissociation. In thelatter embodiments, the coagulation electrode(s) may be configured suchthat a single voltage can be applied to coagulate tissue with thecoagulation electrode(s), and to ablate or contract the tissue with theactive electrode(s). In other embodiments, the power supply is combinedwith the probe such that the coagulation electrode receives power whenthe power supply is in the coagulation mode (low voltage), and theactive electrode(s) receive power when the power supply is in theablation mode (higher voltage).

In a method according to one embodiment of the present invention, one ormore active electrodes are brought into close proximity to tissue at atarget site, and the power supply is activated in the ablation mode suchthat sufficient voltage is applied between the active electrodes and thereturn electrode to volumetrically remove the tissue through moleculardissociation, as described below. During this process, vessels withinthe tissue will be severed. Smaller vessels will be automatically sealedwith the system and method of the present invention. Larger vessels, andthose with a higher flow rate, such as arterial vessels, may not beautomatically sealed in the ablation mode. In these cases, the severedvessels may be sealed by activating a control (e.g., a foot pedal) toreduce the voltage of the power supply and to convert the system intothe coagulation mode. In this mode, the active electrodes may be pressedagainst the severed vessel to provide sealing and/or coagulation of thevessel. Alternatively, a coagulation electrode located on the same or adifferent probe may be pressed against the severed vessel. Once thevessel is adequately sealed, the surgeon activates a control (e.g.,another foot pedal) to increase the voltage of the power supply andconvert the system back into the ablation mode.

The present invention is also useful for removing or ablating tissuearound nerves, such as spinal or cranial nerves, e.g., the olfactorynerve on either side of the nasal cavity, the optic nerve within theoptic and cranial canals, and the palatine nerve within the nasalcavity, soft palate, uvula and tonsil, etc. One of the significantdrawbacks with prior art microdebriders and lasers is that these devicesdo not differentiate between the target tissue and the surroundingnerves or bone. Therefore, the surgeon must be extremely careful duringthese procedures to avoid damage to the bone or nerves within and aroundthe nasal cavity. In the present invention, the Coblation® process forremoving tissue results in extremely small depths of collateral tissuedamage as discussed above. This allows the surgeon to remove tissueclose to a nerve without causing collateral damage to the nerve fibers.

In addition to the generally precise nature of the novel mechanisms ofthe present invention, applicant has discovered an additional method ofensuring that adjacent nerves are not damaged during tissue removal.According to the present invention, systems and methods are provided fordistinguishing between the fatty tissue immediately surrounding nervefibers and the normal tissue that is to be removed during the procedure.Peripheral nerves usually comprise a connective tissue sheath, orepineurium, enclosing the bundles of nerve fibers to protect these nervefibers. This protective tissue sheath typically comprises a fatty tissue(e.g., adipose tissue) having substantially different electricalproperties than the normal target tissue, such as the turbinates,polyps, mucous tissue or the like, that are, for example, removed fromthe nose during sinus procedures. The system of the present inventionmeasures the electrical properties of the tissue at the tip of the probewith one or more active electrode(s). These electrical properties mayinclude electrical conductivity at one, several or a range offrequencies (e.g., in the range from 1 kHz to 100 MHz), dielectricconstant, capacitance or combinations of these. In this embodiment, anaudible signal may be produced when the sensing electrode(s) at the tipof the probe detects the fatty tissue surrounding a nerve, or directfeedback control can be provided to only supply power to the activeelectrode(s), either individually or to the complete array ofelectrodes, if and when the tissue encountered at the tip or working endof the probe is normal tissue based on the measured electricalproperties.

In one embodiment, the current limiting elements (discussed in detailbelow) are configured such that the active electrodes will shut down orturn off when the electrical impedance of tissue at the tip of the probereaches a threshold level. When this threshold level is set to theimpedance of the fatty tissue surrounding nerves, the active electrodeswill shut off whenever they come in contact with, or in close proximityto, nerves. Meanwhile, the other active electrodes, which are in contactwith or in close proximity to nasal tissue, will continue to conductelectric current to the return electrode. This selective ablation orremoval of lower impedance tissue in combination with the Coblation®mechanism of the present invention allows the surgeon to preciselyremove tissue around nerves or bone.

In addition to the above, applicant has discovered that the Coblation®mechanism of the present invention can be manipulated to ablate orremove certain tissue structures, while having little effect on othertissue structures. As discussed above, the present invention uses atechnique of vaporizing electrically conductive fluid to form a plasmalayer or pocket around the active electrode(s), and then inducing thedischarge of energy from this plasma or vapor layer to break themolecular bonds of the tissue structure. Based on initial experiments,applicants believe that the free electrons within the ionized vaporlayer are accelerated in the high electric fields near the electrodetip(s). When the density of the vapor layer (or within a bubble formedin the electrically conductive liquid) becomes sufficiently low (i.e.,less than approximately 10²⁰ atoms/cm³ for aqueous solutions), theelectron mean free path increases to enable subsequently injectedelectrons to cause impact ionization within these regions of low density(i.e., vapor layers or bubbles). Energy evolved by the energeticelectrons (e.g., 4 to 5 eV) can subsequently bombard a molecule andbreak its bonds, dissociating a molecule into free radicals, which thencombine to form gaseous or liquid Coblation® by-products.

The energy evolved by the energetic electrons may be varied by adjustinga variety of factors, such as: the number of active electrodes;electrode size and spacing; electrode surface area; asperities and sharpedges on the electrode surfaces; electrode materials; applied voltageand power; current limiting means, such as inductors; electricalconductivity of the fluid in contact with the electrodes; density of thefluid; and other factors. Accordingly, these factors can be manipulatedto control the energy level of the excited electrons. Since differenttissue structures have different molecular bonds, the present inventioncan be configured to break the molecular bonds of certain tissue, whilehaving too low an energy to break the molecular bonds of other tissue.For example, components of adipose tissue have double bonds that requirea substantially higher energy level than 4 to 5 eV to break.Accordingly, the present invention in its current configurationgenerally does not ablate or remove such fatty tissue. However, thepresent invention may be used to effectively ablate cells to release theinner fat content in a liquid form. Of course, factors may be changedsuch that these double bonds can be broken (e.g., increasing the voltageor changing the electrode configuration to increase the current densityat the electrode tips).

In another aspect of the invention, a loop electrode is employed toresect, shape or otherwise remove tissue fragments from the treatmentsite, and one or more active electrodes are employed to ablate (i.e.,break down the tissue by processes including molecular dissociation ordisintegration) the non-ablated tissue fragments in situ. Once a tissuefragment is cut, partially ablated or resected by the loop electrode,one or more active electrodes will be brought into close proximity tothese fragments (either by moving the probe into position, or by drawingthe fragments to the active electrodes with a suction lumen). Voltage isapplied between the active electrodes and the return electrode tovolumetrically remove the fragments through molecular dissociation, asdescribed above. The loop electrode and the active electrodes arepreferably electrically isolated from each other such that, for example,current can be limited (passively or actively) or completely interruptedto the loop electrode as the surgeon employs the active electrodes toablate tissue fragments (and vice versa).

In another aspect of the invention, the loop electrode(s) are employedto ablate tissue using the Coblation® mechanisms described above. Inthese embodiments, the loop electrode(s) provides a relatively uniformsmooth cutting or ablation effect across the tissue. In addition, loopelectrodes generally have a larger surface area exposed to electricallyconductive fluid (as compared to the smaller active electrodes describedabove), which increases the rate of ablation of tissue. Preferably, theloop electrode(s) extend a sufficient distance from the electrodesupport member selected to achieve a desirable ablation rate, whileminimizing power dissipation into the surrounding medium (which couldcause undesirable thermal damage to surrounding or underlying tissue).In an exemplary embodiment, the loop electrode has a length from one endto the other end of about 0.5 to 20 mm, usually about 1 to 8 mm. Theloop electrode usually extends about 0.25 to 10 mm from the distal endof the support member, preferably about 1 to 4 mm.

The loop electrode(s) may have a variety of cross-sectional shapes.Electrode shapes according to the present invention can include the useof formed wire (e.g., by drawing round wire through a shaping die) toform electrodes with a variety of cross-sectional shapes, such assquare, rectangular, L or V shaped, or the like. Electrode edges mayalso be created by removing a portion of the elongate metal electrode toreshape the cross-section. For example, material can be removed alongthe length of a solid or hollow wire electrode to form D or C shapedwires, respectively, with edges facing in the cutting direction.Alternatively, material can be removed at closely spaced intervals alongthe electrode length to form transverse grooves, slots, threads or thelike along the electrodes.

In some embodiments, the loop electrode(s) will have a “non-active”portion or surface to selectively reduce undesirable current flow fromthe non-active portion or surface into tissue or surroundingelectrically conductive liquids (e.g., isotonic saline, blood, orblood/non-conducting irrigant mixtures). Preferably, the “non-active”electrode portion will be coated with an electrically insulatingmaterial. This can be accomplished, for example, with plasma depositedcoatings of an insulating material, thin-film deposition of aninsulating material using evaporative or sputtering techniques (e.g.,SiO₂ or Si₃N₄), dip coating, or by providing an electrically insulatingsupport member to electrically insulate a portion of the externalsurface of the electrode. The electrically insulated non-active portionof the active electrode(s) allows the surgeon to selectively resectand/or ablate tissue, while minimizing necrosis or ablation ofsurrounding non-target tissue or other body structures.

In addition, the loop electrode(s) may comprise a single electrodeextending from first and second ends to an insulating support in theshaft, or multiple, electrically isolated electrodes extending aroundthe loop. One or more return electrodes may also be positioned along theloop portion. Further descriptions of these configurations can be foundin U.S. application Ser. No. 08/687,792, filed on Jul. 18, 1996, nowU.S. Pat. No. 5,843,019, which as already been incorporated herein byreference.

The electrosurgical probe will comprise a shaft or a handpiece having aproximal end and a distal end which supports one or more activeelectrode(s). The shaft or handpiece may assume a wide variety ofconfigurations, with the primary purpose being to mechanically supportthe active electrode and permit the treating physician to manipulate theelectrode from a proximal end of the shaft. The shaft may be rigid orflexible, with flexible shafts optionally being combined with agenerally rigid external tube for mechanical support. The distal portionof the shaft may comprise a flexible material, such as plastics,malleable stainless steel, etc, so that the physician can mold thedistal portion into different configurations for different applications.Flexible shafts may be combined with pull wires, shape memory actuators,and other known mechanisms for effecting selective deflection of thedistal end of the shaft to facilitate positioning of the electrodearray. The shaft will usually include a plurality of wires or otherconductive elements running axially therethrough to permit connection ofthe electrode array to a connector at the proximal end of the shaft.Thus, the shaft will typically have a length of at least 5 cm for oralprocedures and at least 10 cm, more typically being 20 cm, or longer forendoscopic procedures. The shaft will typically have a diameter of atleast 0.5 mm and frequently in the range of from about 1 to 10 mm. Ofcourse, for dermatological procedures on the outer skin, the shaft mayhave any suitable length and diameter that would facilitate handling bythe surgeon.

For procedures within the nose and joints, the shaft will have asuitable diameter and length to allow the surgeon to reach the target bydelivering the probe shaft through a percutaneous opening in the patient(e.g., a portal formed in the joint in arthroscopic surgery, or throughone of the patient's nasal passages in FESS). Thus, the shaft willusually have a length in the range of from about 5 to 25 cm, and adiameter in the range of from about 0.5 to 5 mm. For proceduresrequiring the formation of a small hole or channel in tissue, such astreating swollen turbinates, the shaft diameter will usually be lessthan 3 mm, preferably less than about 1 mm. Likewise, for procedures inthe ear, the shaft should have a length in the range of about 3 to 20cm, and a diameter of about 0.3 to 5 mm. For procedures in the mouth orupper throat, the shaft will have any suitable length and diameter thatwould facilitate handling by the surgeon. For procedures in the lowerthroat, such as laryngectomies, the shaft will be suitably designed toaccess the larynx. For example, the shaft may be flexible, or have adistal bend to accommodate the bend in the patient's throat. In thisregard, the shaft may be a rigid shaft having a specifically designedbend to correspond with the geometry of the mouth and throat, or it mayhave a flexible distal end, or it may be part of a catheter. In any ofthese embodiments, the shaft may also be introduced through rigid orflexible endoscopes. Specific shaft designs will be described in detailin connection with the figures hereinafter.

The current flow path between the active electrode(s) and the returnelectrode(s) may be generated by submerging the tissue site in anelectrically conductive fluid (e.g., a viscous fluid, such as anelectrically conductive gel), or by directing an electrically conductivefluid along a fluid path to the target site (i.e., a liquid, such asisotonic saline, or a gas, such as argon). This latter method isparticularly effective in a dry environment (i.e., the tissue is notsubmerged in fluid) because the electrically conductive fluid provides asuitable current flow path from the active electrode to the returnelectrode. A more complete description of an exemplary method ofdirecting electrically conductive fluid between the active and returnelectrodes is described in commonly assigned U.S. patent applicationSer. No. 08/485,219, filed Jun. 7, 1995, now U.S. Pat. No. 5,697,281,the contents of which are incorporated by reference herein in theirentirety for all purposes.

In some procedures, it may also be necessary to retrieve or aspirate theelectrically conductive fluid after it has been directed to the targetsite. For example, in procedures in the nose, mouth or throat, it may bedesirable to aspirate the fluid so that it does not flow down thepatient's throat. In addition, it may be desirable to aspirate smallpieces of tissue that are not completely disintegrated by the highfrequency energy, air bubbles, or other fluids at the target site, suchas blood, mucus, the gaseous products of ablation, etc. Accordingly, thesystem of the present invention can include a suction lumen in theprobe, or on another instrument, for aspirating fluids from the targetsite.

In some embodiments, the probe will include one or more aspirationelectrode(s) coupled to the distal end of the suction lumen forablating, or at least reducing the volume of, tissue fragments that areaspirated into the lumen. The aspiration electrode(s) function mainly toinhibit clogging of the lumen that may otherwise occur as larger tissuefragments are drawn therein. The aspiration electrode(s) may bedifferent from the ablation active electrode(s), or the sameelectrode(s) may serve both functions. In some embodiments, the probewill be designed to use suction force to draw loose tissue, such assynovial tissue to the aspiration or ablation electrode(s) on the probe,which are then energized to ablate the loose tissue.

In other embodiments, the aspiration lumen can be positioned proximal ofthe active electrodes a sufficient distance such that the aspirationlumen will primarily aspirate air bubbles and body fluids such as blood,mucus, or the like. Such a configuration allows the electricallyconductive fluid to dwell at the target site for a longer period.Consequently, the plasma can be created more aggressively at the targetsite and the tissue can be treated in a more efficient manner.Additionally, by positioning the aspiration lumen opening somewhatdistant from the active electrodes, it may not be necessary to haveablation electrodes at the lumen opening since, in this configuration,tissue fragments will typically not be aspirated through the lumen.

The present invention may use a single active electrode or an electrodearray distributed over a contact surface of a probe. In the latterembodiment, the electrode array usually includes a plurality ofindependently current-limited and/or power-controlled active electrodesto apply electrical energy selectively to the target tissue whilelimiting the unwanted application of electrical energy to thesurrounding tissue and environment. Such unwanted application ofelectrical energy results from power dissipation into surroundingelectrically conductive liquids, such as blood, normal saline,electrically conductive gel and the like. The active electrodes may beindependently current-limited by isolating the terminals from each otherand connecting each terminal to a separate power source that is isolatedfrom the other active electrodes. Alternatively, the active electrodesmay be connected to each other at either the proximal or distal ends ofthe probe to form a single connector that couples to a power source.

In one configuration, each individual active electrode in the electrodearray is electrically insulated from all other active electrodes in thearray within the probe and is connected to a power source which isisolated from each of the other active electrodes in the array or tocircuitry which limits or interrupts current flow to the activeelectrode when low resistivity material (e.g., blood, electricallyconductive saline irrigant or electrically conductive gel) causes alower impedance path between the return electrode and the individualactive electrode. The isolated power sources for each individual activeelectrode may be separate power supply circuits having internalimpedance characteristics which limit power to the associated activeelectrode when a low impedance return path is encountered. By way ofexample, the isolated power source may be a user selectable constantcurrent source. In this embodiment, lower impedance paths willautomatically result in lower resistive heating levels since the heatingis proportional to the square of the operating current times theimpedance. Alternatively, a single power source may be connected to eachof the active electrodes through independently actuatable switches, orby independent current limiting elements, such as inductors, capacitors,resistors and/or combinations thereof. The current limiting elements maybe provided in the probe, connectors, cable, controller, or along theconductive path from the controller to the distal tip of the probe.Alternatively, the resistance and/or capacitance may occur on thesurface of the active electrode(s) due to oxide layers which formselected active electrodes (e.g., titanium or a resistive coating on thesurface of metal, such as platinum).

The tip region of the probe may comprise many independent activeelectrodes designed to deliver electrical energy in the vicinity of thetip. The selective application of electrical energy to the conductivefluid is achieved by connecting each individual active electrode and thereturn electrode to a power source having independently controlled orcurrent limited channels. The return electrode(s) may comprise a singletubular member of conductive material proximal to the electrode array atthe tip which also serves as a conduit for the supply of theelectrically conductive fluid between the active and return electrodes.Alternatively, the probe may comprise an array of return electrodes atthe distal tip of the probe (together with the active electrodes) tomaintain the electric current at the tip. The application of highfrequency voltage between the return electrode(s) and the electrodearray results in the generation of high electric field intensities atthe distal tips of the active electrodes with conduction of highfrequency current from each individual active electrode to the returnelectrode. The current flow from each individual active electrode to thereturn electrode(s) is controlled by either active or passive means, ora combination thereof, to deliver electrical energy to the surroundingconductive fluid while minimizing energy delivery to surrounding(non-target) tissue.

The application of a high frequency voltage between the returnelectrode(s) and the active electrode(s) for appropriate time intervalseffects cutting, removing, ablating, shaping, contracting or otherwisemodifying the target tissue. The tissue volume over which energy isdissipated (i.e., over which a high current density exists) may beprecisely controlled, for example, by the use of a multiplicity of smallactive electrodes whose effective diameters or principal dimensionsrange from about 5 mm to 0.01 mm, preferably from about 2 mm to 0.05 mm,and more preferably from about 1 mm to 0.1 mm. In these embodiments,electrode areas for both circular and non-circular terminals will have acontact area (per active electrode) below 25 mm², preferably being inthe range from 0.0001 mm² to 1 mm², and more preferably from 0.005 mm²to 0.5 mm². The circumscribed area of the electrode array is in therange from 0.25 mm² to 75 mm², preferably from 0.5 mm to 40 mm², andwill usually include at least two isolated active electrodes, preferablyat least five active electrodes, often greater than 10 active electrodesand even 50 or more active electrodes, disposed over the distal contactsurfaces on the shaft. The use of small diameter active electrodesincreases the electric field intensity and reduces the extent or depthof tissue heating as a consequence of the divergence of current fluxlines which emanate from the exposed surface of each active electrode.

The area of the tissue treatment surface can vary widely, and the tissuetreatment surface can assume a variety of geometries, with particularareas and geometries being selected for specific applications. Activeelectrode surfaces can have areas in the range from 0.25 mm² to 75 mm²,usually being from about 0.5 mm² to 40 mm². The geometries can beplanar, concave, convex, hemispherical, conical, linear “in-line” arrayor virtually any other regular or irregular shape. Most commonly, theactive electrode(s) or active electrode(s) will be formed at the distaltip of the electrosurgical probe shaft, frequently being planar,disk-shaped, or hemispherical surfaces for use in reshaping proceduresor being linear arrays for use in cutting. Alternatively oradditionally, the active electrode(s) may be formed on lateral surfacesof the electrosurgical probe shaft (e.g., in the manner of a spatula),facilitating access to certain body structures in endoscopic procedures.

The electrically conductive fluid should have a threshold conductivityto provide a suitable conductive path between the active electrode(s)and the return electrode(s). The electrical conductivity of the fluid(in units of millisiemens per centimeter or mS/cm) will usually begreater than 0.2 mS/cm, preferably will be greater than 2 mS/cm and morepreferably greater than 10 mS/cm. In an exemplary embodiment, theelectrically conductive fluid is isotonic saline, which has aconductivity of about 17 mS/cm.

In some embodiments, the electrode support and the fluid outlet may berecessed from an outer surface of the probe or handpiece to confine theelectrically conductive fluid to the region immediately surrounding theelectrode support. In addition, the shaft may be shaped so as to form acavity around the electrode support and the fluid outlet. This helps toassure that the electrically conductive fluid will remain in contactwith the active electrode(s) and the return electrode(s) to maintain theconductive path therebetween. In addition, this will help to maintain avapor or plasma layer between the active electrode(s) and the tissue atthe treatment site throughout the procedure, which reduces the thermaldamage that might otherwise occur if the vapor layer were extinguisheddue to a lack of conductive fluid. Provision of the electricallyconductive fluid around the target site also helps to maintain thetissue temperature at desired levels.

The voltage applied between the return electrode(s) and the electrodearray will be at high or radio frequency, typically between about 5 kHzand 20 MHz, usually being between about 30 kHz and 2.5 MHz, preferablybeing between about 50 kHz and 500 kHz, more preferably less than 350kHz, and most preferably between about 100 kHz and 200 kHz. The RMS(root mean square) voltage applied will usually be in the range fromabout 5 volts to 1000 volts, preferably being in the range from about 10volts to 500 volts depending on the active electrode size, the operatingfrequency and the operation mode of the particular procedure or desiredeffect on the tissue (i.e., contraction, coagulation or ablation).Typically, the peak-to-peak voltage will be in the range of 10 to 2000volts, preferably in the range of 20 to 1200 volts and more preferablyin the range of about 40 to 800 volts (again, depending on the electrodesize, the operating frequency and the operation mode).

As discussed above, the voltage is usually delivered in a series ofvoltage pulses or alternating current of time varying voltage amplitudewith a sufficiently high frequency (e.g., on the order of 5 kHz to 20MHz) such that the voltage is effectively applied continuously (ascompared with e.g., lasers claiming small depths of necrosis, which aregenerally pulsed at about 10 to 20 Hz). In addition, the duty cycle(i.e., cumulative time in any one-second interval that energy isapplied) is on the order of about 50% for the present invention, ascompared with pulsed lasers which typically have a duty cycle of about0.0001%.

The preferred power source of the present invention delivers a highfrequency current selectable to generate average power levels rangingfrom several milliwatts to tens of watts per electrode, depending on thevolume of target tissue being heated, and/or the maximum allowedtemperature selected for the probe tip. The power source allows the userto select the voltage level according to the specific requirements of aparticular FESS procedure, arthroscopic surgery, dermatologicalprocedure, ophthalmic procedures, open surgery or other endoscopicsurgery procedure. A description of a suitable power source can be foundin U.S. Patent Application No. 60/062,997, filed Oct. 23, 1997, thecomplete disclosure of which has been incorporated herein by reference.

The power source may be current limited or otherwise controlled so thatundesired heating of the target tissue or surrounding (non-target)tissue does not occur. In one embodiment of the present invention,current limiting inductors are placed in series with each independentactive electrode, where the inductance of the inductor is in the rangeof 10uH to 50,000uH, depending on the electrical properties of thetarget tissue, the desired tissue heating rate, and the operatingfrequency. Alternatively, capacitor-inductor (LC) circuit structures maybe employed, as described previously in co-pending PCT application No.PCT/US94/05168, the complete disclosure of which is incorporated hereinby reference. Additionally, current limiting resistors may be selected.Preferably, these resistors will have a large positive temperaturecoefficient of resistance so that, as the current level begins to risefor any individual active electrode in contact with a low resistancemedium (e.g., saline irrigant or conductive gel), the resistance of thecurrent limiting resistor increases significantly, thereby minimizingthe power delivery from the active electrode into the low resistancemedium (e.g., saline irrigant or conductive gel).

It should be clearly understood that the invention is not limited toelectrically isolated active electrodes, or even to a plurality ofactive electrodes. For example, the array of active electrodes may beconnected to a single lead that extends through the probe shaft to apower source of high frequency current. Alternatively, the probe mayincorporate a single electrode that extends directly through the probeshaft or is connected to a single lead that extends to the power source.The active electrode may have a ball shape (e.g., for tissuevaporization and desiccation), a twizzle shape (for vaporization andneedle-like cutting), a spring shape (for rapid tissue debulking anddesiccation), a twisted metal shape, an annular or solid tube shape orthe like. Alternatively, the electrode may comprise a plurality offilaments, a rigid or flexible brush electrode (for debulking a tumor,such as a fibroid, bladder tumor or a prostate adenoma), a side-effectbrush electrode on a lateral surface of the shaft, a coiled electrode orthe like. In one embodiment, the probe comprises a single activeelectrode that extends from an insulating member, e.g., ceramic, at thedistal end of the probe. The insulating member is preferably a tubularstructure that separates the active electrode from a tubular or annularreturn electrode positioned proximal to the insulating member and theactive electrode.

Referring now to FIG. 2, an exemplary electrosurgical system 411 fortreatment of tissue in ‘dry fields’ will now be described in detail. Ofcourse, system 411 may also be used in a ‘wet field’, i.e., the targetsite is immersed in electrically conductive fluid. However, this systemis particularly useful in ‘dry fields’ where the fluid is preferablydelivered through an electrosurgical probe to the target site. As shown,electrosurgical system 411 generally comprises an electrosurgicalhandpiece or probe 410 connected to a power supply 428 for providinghigh frequency voltage to a target site and a fluid source 421 forsupplying electrically conductive fluid 450 to probe 410. In addition,electrosurgical system 411 may include an endoscope (not shown) with afiber optic head light for viewing the surgical site, particularly insinus procedures or procedures in the ear or the back of the mouth. Theendoscope may be integral with probe 410, or it may be part of aseparate instrument. The system 411 may also include a vacuum source(not shown) for coupling to a suction lumen or tube in the probe 410 foraspirating the target site.

As shown, probe 410 generally includes a proximal handle 419 and anelongate shaft 418 having an array 412 of active electrodes 458 at itsdistal end. A connecting cable 434 has a connector 426 for electricallycoupling the active electrodes 458 to power supply 428. The activeelectrodes 458 are electrically isolated from each other and each of theterminals 458 is connected to an active or passive control networkwithin power supply 428 by means of a plurality of individuallyinsulated conductors (not shown). A fluid supply tube 415 is connectedto a fluid tube 414 of probe 410 for supplying electrically conductivefluid 450 to the target site.

Similar to the above embodiment, power supply 428 has an operatorcontrollable voltage level adjustment 430 to change the applied voltagelevel, which is observable at a voltage level display 432. Power supply428 also includes first, second and third foot pedals 437, 438, 439 anda cable 436 which is removably coupled to power supply 428. The footpedals 437, 438, 439 allow the surgeon to remotely adjust the energylevel applied to active electrodes 458. In an exemplary embodiment,first foot pedal 437 is used to place the power supply into the ablationmode and second foot pedal 438 places power supply 428 into the“coagulation” mode. The third foot pedal 439 allows the user to adjustthe voltage level within the “ablation” mode. In the ablation mode, asufficient voltage is applied to the active electrodes to establish therequisite conditions for molecular dissociation of the tissue (i.e.,vaporizing a portion of the electrically conductive fluid, ionizingcharged particles within the vapor layer, and accelerating these chargedparticles against the tissue). As discussed above, the requisite voltagelevel for ablation will vary depending on the number, size, shape andspacing of the electrodes, the distance to which the electrodes extendfrom the support member, etc. Once the surgeon places the power supplyin the ablation mode, voltage level adjustment 430 or third foot pedal439 may be used to adjust the voltage level to adjust the degree oraggressiveness of the ablation.

Of course, it will be recognized that the voltage and modality of thepower supply may be controlled by other input devices. However,applicant has found that foot pedals are convenient methods ofcontrolling the power supply while manipulating the probe during asurgical procedure.

In the coagulation mode, the power supply 428 applies a low enoughvoltage to the active electrodes (or the coagulation electrode) to avoidvaporization of the electrically conductive fluid and subsequentmolecular dissociation of the tissue. The surgeon may automaticallytoggle the power supply between the ablation and coagulation modes byalternately stepping on foot pedals 437, 438, respectively. This allowsthe surgeon to quickly move between coagulation and ablation in situ,without having to remove his/her concentration from the surgical fieldor without having to request an assistant to switch the power supply. Byway of example, as the surgeon is sculpting soft tissue in the ablationmode, the probe typically will simultaneously seal and/or coagulatesmall severed vessels within the tissue. However, larger vessels, orvessels with high fluid pressures (e.g., arterial vessels) may not besealed in the ablation mode. Accordingly, the surgeon can simply actuatefoot pedal 438, automatically lowering the voltage level below thethreshold level for ablation, and apply sufficient pressure onto thesevered vessel for a sufficient period of time to seal and/or coagulatethe vessel. After this is completed, the surgeon may quickly move backinto the ablation mode by actuating foot pedal 437. A specific design ofa suitable power supply for use with the present invention can be foundin Provisional Patent Application No. 60/062,997 filed Oct. 23, 1997,previously incorporated herein by reference.

FIGS. 3 and 4 illustrate an exemplary electrosurgical probe 490constructed according to the principles of the present invention. Asshown in FIG. 3, probe 490 generally includes an elongated shaft 500which may be flexible or rigid, a handle 604 coupled to the proximal endof shaft 500 and an electrode support member 502 coupled to the distalend of shaft 500. Shaft 500 preferably includes a bend 501 that allowsthe distal section of shaft 500 to be offset from the proximal sectionand handle 604. This offset facilitates procedures that require anendoscope, such as FESS, because the endoscope can, for example, beintroduced through the same nasal passage as the shaft 500 withoutinterference between handle 604 and the eyepiece of the endoscope. Inone embodiment, shaft 500 preferably comprises a plastic material thatis easily molded into the desired shape.

In an alternative embodiment (not shown), shaft 500 comprises anelectrically conducting material, usually metal, which is selected fromthe group comprising tungsten, stainless steel alloys, platinum or itsalloys, titanium or its alloys, molybdenum or its alloys, and nickel orits alloys. In this embodiment, shaft 500 includes an electricallyinsulating jacket 508 which is typically formed as one or moreelectrically insulating sheaths or coatings, such aspolytetrafluoroethylene, polyimide, and the like. The provision of theelectrically insulating jacket over the shaft prevents direct electricalcontact between these metal elements and any adjacent body structure orthe surgeon. Such direct electrical contact between a body structure(e.g., tendon) and an exposed electrode could result in unwanted heatingand necrosis of the structure at the point of contact.

Handle 604 typically comprises a plastic material that is easily moldedinto a suitable shape for handling by the surgeon. Handle 604 defines aninner cavity (not shown) that houses the electrical connections 650(FIG. 4), and provides a suitable interface for connection to anelectrical connecting cable 422 (see FIG. 2). Electrode support member502 extends from the distal end of shaft 500 (usually about 1 to 20 mm),and provides support for a plurality of electrically isolated activeelectrodes 504. As shown in FIG. 3, a fluid tube 633 extends through anopening in handle 604, and includes a connector 635 for connection to afluid supply source, for supplying electrically conductive fluid to thetarget site. Depending on the configuration of the distal surface ofshaft 500, fluid tube 633 may extend through a single lumen (not shown)in shaft 500, or it may be coupled to a plurality of lumens (also notshown) that extend through shaft 500 to a plurality of openings at itsdistal end. In the representative embodiment, fluid tube 633 extendsalong the exterior of shaft 500 to a point just proximal of returnelectrode 512. In this embodiment, the fluid is directed through anopening 637 past return electrode 512 to the active electrodes 504.Probe 490 may also include a valve 417 (FIG. 3) or equivalent structurefor controlling the flow rate of the electrically conductive fluid tothe target site.

In several variations of the invention, a return electrode is notdirectly connected to the active electrode or. To complete this currentpath so that active electrode(s) are electrically connected to returnelectrode, electrically conductive fluid (e.g., isotonic saline) iscaused to flow therebetween. The electrically conductive fluid may bedelivered through a fluid tube (see, e.g., FIG. 3, element 633) to anopening near the distal end of the device. Alternatively, the fluid maybe delivered by a fluid delivery element that is separate from probe. Inarthroscopic surgery, for example, the joint cavity will be flooded withisotonic saline and the probe will be introduced into this floodedcavity. Electrically conductive fluid will be continually resupplied tomaintain the conduction path between return electrode and activeelectrodes.

In alternative embodiments, the fluid path may be formed in probe by,for example, an inner lumen or an annular gap between the returnelectrode and a tubular support member within a shaft of the device.This annular gap may be formed near the perimeter of the shaft such thatthe electrically conductive fluid tends to flow radially inward towardsthe target site, or it may be formed towards the center of the shaft sothat the fluid flows radially outward. In both of these embodiments, afluid source (e.g., a bag of fluid elevated above the surgical site orhaving a pumping device), is coupled to probe via a fluid supply tubethat may or may not have a controllable valve. A more completedescription of an electrosurgical probe incorporating one or more fluidlumen(s) can be found in parent patent application Ser. No. 08/485,219,filed on Jun. 7, 1995, now U.S. Pat. No. 5,697,281, the completedisclosure of which is incorporated herein by reference.

FIG. 4 illustrates the electrical connections 650 within handle 604 forcoupling active electrodes 504 and return electrode 512 to the powersupply 428. As shown, a plurality of wires 652 extend through shaft 500to couple terminals 504 to a plurality of pins 654, which are pluggedinto a connector block 656 for coupling to a connecting cable 422 (FIG.2). Similarly, return electrode 512 is coupled to connector block 656via a wire 658 and a plug 660. Alternatively, the device may have anintegrated cable fixedly attached to the connections where the proximalportion of the cable (the end of the cable opposite to the device)contains connections allowing for coupling of the device to a powersupply.

FIGS. 5-9 illustrate another embodiment of the present invention. Asshown in FIG. 5, an electrosurgical probe 800 includes an elongatedshaft 801 which may be flexible or rigid, a handle 804 coupled to theproximal end of shaft 801 and an electrode support member 802 coupled tothe distal end of shaft 801. As in previous embodiments, probe 800includes an active loop electrode 803 (e.g., FIG. 7) and a returnelectrode 812 (not shown), the latter spaced proximally from active loopelectrode 803. The probe 800 further includes a suction lumen 820 (FIG.6) for aspirating excess fluids, bubbles, tissue fragments, and/orproducts of ablation from the target site. As shown in FIGS. 6 and 9,suction lumen 820 extends through support member 802 to a distal opening822, and extends through shaft 801 and handle 804 to an externalconnector 824 for coupling to a vacuum source. Typically, the vacuumsource is a standard hospital pump that provides suction pressure toconnector 824 and lumen 820.

As shown in FIG. 6, handle 804 defines an inner cavity 808 that housesthe electrical connections 850 (discussed above), and provides asuitable interface for connection to an electrical connecting cable 22(see FIG. 1). As shown in FIG. 8, the probe will also include a codingresistor 860 having a value selected to program different output rangesand modes of operation for the power supply. This allows a single powersupply to be used with a variety of different probes in differentapplications (e.g., dermatology, cardiac surgery, neurosurgery,arthroscopy, etc).

Electrode support member 802 extends from the distal end of shaft 801(usually about 1 to 20 mm), and provides support for loop electrode 803and a ring electrode 804 (see FIG. 9). As shown in FIG. 7, loopelectrode 803 has first and second ends extending from the electrodesupport member 802. The first and second ends are each coupled to, orintegral with, one or more connectors, e.g., wires (not shown), thatextend through the shaft of the probe to its proximal end for couplingto the high frequency power supply. The loop electrode usually extendsabout 0.5 to about 10 mm from the distal end of support member,preferably about 1 to 2 mm. Loop electrode 803 usually extends furtheraway from the support member than the ring electrode 804 to facilitateablation of tissue. As discussed below, loop electrode 803 is especiallyconfigured for tissue ablation, while the ring electrode 804 ablatestissue fragments that are aspirated into suction lumen 820.

Referring to FIG. 9, ring electrode 804 preferably comprises a tungstenor titanium wire having two ends 830, 832 coupled to electricalconnectors (not shown) within support member 802. The wire is bent toform one-half of a figure eight, thereby forming a ring positioned overopening 822 of suction lumen 820. This ring inhibits passage of tissuefragments large enough to clog suction lumen 820. Moreover, voltagesapplied between ring electrode 804 and return electrode 812 providesufficient energy to ablate these tissue fragments into smallerfragments that are then aspirated through lumen 820. In a presentlypreferred embodiment, ring electrode 804 and loop electrode 803 areelectrically isolated from each other. However, electrodes 804, 803 maybe electrically coupled to each other in some applications.

The systems of the present invention may include a bipolar arrangementof electrodes designed to ablate tissue at the target site, and thenaspirate tissue fragments, as described above. Alternatively, theinstrument may also include a rotating shaft with a cutting tip forcutting tissue in a conventional manner. In this embodiment, theelectrode(s) serve to effect hemostasis at the target site and to reduceclogging of the aspiration lumen, while the rotating shaft and cuttingtip do the bulk of tissue removal by cutting the tissue in aconventional manner.

The system and method of the present invention may also be useful toefficaciously ablate (i.e., disintegrate) cancer cells and tissuecontaining cancer cells, such as cancer on the surface of the epidermis,eye, colon, bladder, cervix, uterus and the like. The presentinvention's ability to completely disintegrate the target tissue can beadvantageous in this application because simply vaporizing andfragmenting cancerous tissue may lead to spreading of viable cancercells (i.e., seeding) to other portions of the patient's body or to thesurgical team in close proximity to the target tissue. In addition, thecancerous tissue can be removed to a precise depth while minimizingnecrosis of the underlying tissue.

In another aspect, the present invention provides an electrosurgicalprobe having at least one active loop electrode for resecting andablating tissue. In comparison to the planar electrodes, ballelectrodes, or the like, the active loop electrodes provide a greatercurrent concentration to the tissue at the target site. The greatercurrent concentration can be used to aggressively create a plasma withinthe electrically conductive fluid, and hence a more efficient resectionof the tissue at the target site. In use, the loop electrode(s) aretypically employed to ablate tissue using the Coblation® mechanisms asdescribed above. Voltage is applied between the active loop electrodesand a return electrode to volumetrically loosen fragments from thetarget site through molecular dissociation. Once the tissue fragmentsare loosened from the target site, the tissue fragments can be ablatedin situ within the plasma (i.e., break down the tissue by processesincluding molecular dissociation or disintegration).

In some embodiments, the loop electrode(s) provide a relatively uniformsmooth cutting or ablation effect across the tissue. The loop electrodesgenerally have a larger surface area exposed to electrically conductivefluid (as compared to the smaller active electrodes described above),which increases the rate of ablation of tissue.

Applicants have found that the current concentrating effects of the loopelectrodes further provide reduced current dissipation into thesurrounding tissue, and consequently improved patient comfort throughthe reduced stimulation of surrounding nerves and muscle. Preferably,the loop electrode(s) extend a sufficient distance from the electrodesupport member to achieve current concentration and an improved ablationrate while simultaneously reducing current dissipation into thesurrounding medium (which can cause undesirable muscle stimulation,nerve stimulation, or thermal damage to surrounding or underlyingtissue). In an exemplary embodiment, the loop electrode has a lengthfrom one end to the other end of about 0.5 mm to 20 mm, usually about 1mm to 8 mm. The loop electrode usually extends about 0.25 mm to 10 mmfrom the distal end of the support member, preferably about 1 mm to 4mm.

The loop electrode(s) may have a variety of cross-sectional shapes.Electrode shapes according to the present invention can include the useof formed wire (e.g., by drawing round wire through a shaping die) toform electrodes with a variety of cross-sectional shapes, such assquare, rectangular, L or V shaped, or the like. Electrode edges mayalso be created by removing a portion of the elongate metal electrode toreshape the cross-section. For example, material can be removed alongthe length of a solid or hollow wire electrode to form D or C shapedwires, respectively, with edges facing in the cutting direction.Alternatively, material can be removed at closely spaced intervals alongthe electrode length to form transverse grooves, slots, threads or thelike along the electrodes.

In yet another aspect, the present invention provides an electrosurgicalprobe having an aspiration lumen with an opening that is spacedproximally from the active electrodes. Applicants have found that, byspacing the suction lumen opening proximal of the active electrodes, amore aggressive plasma can be created. In use, the saline is deliveredto the target site and allowed to remain in contact with the electrodesand tissue for a longer period of time. By increasing the distancebetween the aspiration lumen and the conductive fluid, the dwell time ofthe conductive fluid is increased and the plasma can be aggressivelycreated. Advantageously, by moving the aspiration lumen out of thetarget area, the suction will primarily aspirate blood and gas bubblesfrom the target site, while leaving the conductive fluid in the targetarea. Consequently, less conductive fluid and tissue fragments areaspirated from the target site and less clogging of the aspiration lumenoccurs.

In a further aspect, the present invent provides an electrosurgicalprobe having a conductive fluid delivery lumen that has at least onedistal opening positioned at least partially around the activeelectrodes. The configuration of the openings can be completely aroundthe active electrodes (e.g., 0 configuration or annular shaped) orpartially around the active electrodes (e.g., U configuration or Cconfiguration) such that delivery of the conductive fluid immerses theactive electrodes with conductive fluid during the ablation or resectionprocedure. Because the conductive fluid can be delivered from aplurality of directions, the dwell time of the conductive fluid isincreased, and consequently the creation of the plasma can be improved.

In a preferred embodiment, the conductive fluid lumen comprises aplurality of openings that are positioned so as to substantiallysurround the active electrode array. As above, by “substantiallysurround”, is meant that the openings are at least partially around theactive electrodes. In some configurations, the openings will be equallyspaced around the active electrodes. However, it will be appreciatedthat in other alternative embodiments, the openings will only partiallysurround the active electrodes or can be unevenly spaced about theactive electrodes.

With reference to FIGS. 12-19I there follows a description of anelectrosurgical probe 1400 including a resection unit 1406, according tovarious embodiments of the instant invention. Probe 1400 is adapted foraggressive ablation, for resection, or for combined ablation andresection of tissue. Probe 1400 may be used in a broad range of surgicalprocedures including, without limitation, those listed or describedhereinabove. In some embodiments, resection unit 1406 may be used toresect tissue by mechanical abrasion, cutting, or severing of tissue. Insome embodiments, resection unit 1406 may be used to ablate tissue,e.g., via a Coblation® (cool ablation) mechanism. The Coblation®mechanism has been described hereinabove. Briefly, and without beingbound by theory, Coblation® involves the localized generation of aplasma by the application of a high frequency voltage between at leastone active electrode and a return electrode in the presence of anelectrically conductive fluid. The plasma thus generated causes thebreakdown of tissues, e.g., via molecular dissociation, to form lowmolecular weight ablation by-products. Such low molecular weightablation by-products may be easily removed from a target site, e.g., viaaspiration. Coblation® allows the controlled removal of tissue, in whichboth the quantity and quality of tissue removed can be accuratelydetermined. In some embodiments, resection unit 1406 may be used forcombined resection and ablation: to resect tissue by application of amechanical force to the tissue and, concurrently therewith, toelectrically ablate (“Coblate”) the tissue contacted by resection unit1406. Applicants have found that a combination of mechanical resectionand electrical ablation by resection unit 1406 provides advantageoustissue removal, as compared with mechanical resection or electricalablation alone. Advantages of tissue removal by combined resection andablation by resection unit 1406 include a more rapid and aggressivetissue removal, as compared with ablation alone; and a more controlledand less traumatic tissue removal, as compared with mechanical resectionalone.

FIG. 12 shows probe 1400 including a shaft 1402 affixed at shaftproximal end portion 1402 b to a handle 1404. Resection unit 1406 isdisposed on shaft distal end portion 1402 a. Although FIG. 12 shows onlya single resection unit 1406 on shaft 1402, certain embodiments of theinstant invention may include a plurality of resection units 1406 whichmay be alike or dissimilar in various respects (for example, the sizeand shape of electrode support 1408, and the number, arrangement, andtype of resection electrodes 1410) (FIG. 13). In the embodiment of FIG.12, a return electrode 1420 is located at shaft distal end portion 1402a. Return electrode 1420 may be in the form of an annular band.Resection unit 1406 is shown in FIG. 12 as being arranged within, orsurrounded by, return electrode 1420. In other embodiments, resectionunit 1406 may be arranged adjacent to return electrode 1420. Under theinvention, shaft 1402 may be provided in a range of different lengthsand diameters. Preferably, shaft 1402 has a length in the range of fromabout 5 cm to about 30 cm; more preferably in the range of from about 10cm to about 25 cm. Preferably, shaft 1402 has a diameter in the range offrom about 1 mm to about 20 mm; more preferably in the range of fromabout 2 mm to about 10 mm.

FIG. 13 schematically represents resection unit 1406 of probe 1400,wherein resection unit 1406 includes a resection electrode 1410 on aresection electrode support member 1408. In FIG. 13 resection electrode1410 is represented as a single “box” located within support 1408,however, other arrangements and numbers of resection electrode 1410 arecontemplated and are within the scope of the invention (see, forexample, FIGS. 16A-F). Resection electrode support 1408 may comprise anelectrically insulating, and durable or refractory material, such as aglass, a ceramic, a silicone, a polyurethane, a urethane, a polyimide,silicon nitride, teflon, or alumina, and the like. Resection electrodesupport 1408 is shown in FIG. 13 as being substantially square inoutline, however, a broad range of other shapes are also possible. Thesize of resection electrode support 1408 may depend on a number offactors, including the diameter or width of shaft 1402. In oneembodiment, support 1408 may be mounted laterally on shaft 1402 as anannular band, i.e., support 1408 may completely encircle shaft 1402.Typically support 1408 represents or occupies from about 2% to 100% ofthe circumference of shaft 1402. More typically, support 1408 occupiesfrom about 50% to 80% of the circumference of shaft 1402, most typicallyfrom about 10% to 50% of the circumference of shaft 1402. In embodimentswherein support 1408 is mounted terminally on shaft 1402, support 1408typically occupies from about 5% to 100% of the cross-sectional area ofshaft 1402, more typically from about 10% to 95% of the cross-sectionalarea of shaft 1402.

FIGS. 14A-D each show an electrosurgical probe 1400, according tocertain embodiments of the invention. Probe 1400 is depicted in FIGS.14A-D as being linear, however, according to various embodiments of theinvention, shaft 1402 may include one or more curves or bends therein(see, for example, FIGS. 34A-B). Resection electrodes 1410 are omittedfrom FIGS. 14A-D for the sake of clarity. However, as describedelsewhere herein, each resection unit 1406 includes at least oneresection electrode 1410 (see, for example, FIGS. 16A-F, 18A-D).

With reference to FIG. 14A, probe 1400 includes a fluid delivery tube1434, and a fluid delivery port 1430 located distal to resection unit1406 on shaft distal end portion 1402 a. Fluid delivery port 1430 iscoupled to fluid delivery tube 1434 via a fluid delivery lumen 1432(FIG. 15B). Fluid delivery tube 1434 is, in turn, coupled to a source ofan electrically conductive fluid (see, e.g., FIG. 2). Fluid deliveryport 1430 is adapted to provide a quantity of an electrically conductivefluid to shaft distal end portion 1402 a during a procedure, as isdescribed elsewhere herein in enabling detail.

FIG. 14B shows probe 1400 including an aspiration tube 1444 and anaspiration port 1440 located proximal to resection unit 1406. In theembodiment depicted in FIG. 14B, aspiration tube 1444 is shown as beingconnected to probe 1400 at shaft proximal end 1402 b, however otherarrangements for coupling aspiration tube 1444 to probe 1400 arepossible under the invention. FIG. 14C shows probe 1400 including bothan aspiration tube 1444 and a fluid delivery tube 1434; and both a fluiddelivery port 1430 and an aspiration port 1440. Although fluid deliveryport 1430 is depicted in FIGS. 14A, 14C as a single port located distalto resection unit 1406, other arrangements of fluid delivery port(s)1430/1430′ with respect to resection unit 1406, are contemplatedaccording to various embodiments of the invention. Aspiration port 1440is located proximal to resection unit 1406. Preferably, aspiration port1440 is located a distance of at least 2 mm proximal to resection unit1406. More preferably, aspiration port 1440 is located a distance in therange of from about 4 mm to about 50 mm proximal to resection unit 1406.In one embodiment, aspiration port 1440 may have a screen (not shown) toprevent relatively large fragments of resected tissue from enteringaspiration lumen 1442 (FIG. 15A). Such a screen may serve as an activeelectrode and cause ablation of tissue fragments which contact thescreen. Alternatively, the screen may serve as a mechanical sieve orfilter to exclude entry of relatively large tissue fragments into lumen1442.

FIG. 14D shows probe 1400 in which resection unit 1406 is located at thedistal terminus of shaft 1402. In this embodiment, return electrode 1420is located at shaft distal end 1402 a, and aspiration port 1440 islocated proximal to return electrode 1420. The embodiment of FIG. 14Dmay further include one or more fluid delivery ports 1430 (see, forexample, FIG. 15B) for delivering an electrically conductive fluid to,at least, resection unit 1406. In certain embodiments, fluid deliveryport(s) 1430 deliver a quantity of an electrically conductive fluid toshaft distal end 1402 a sufficient to immerse resection unit 1406 andreturn electrode 1420. In some embodiments, fluid delivery port(s) 1430deliver a quantity of an electrically conductive fluid from shaft distalend 1402 a sufficient to immerse the tissue at a site targeted forablation and/or resection.

FIG. 15A shows electrosurgical probe 1400 including resection unit 1406and aspiration port 1440 proximal to resection unit 1406, according toone embodiment of the invention. Aspiration port 1440 is coupled toaspiration tube 1444 via an aspiration lumen 1442. Aspiration tube 1444may be coupled to a vacuum source, as is well known in the art.Aspiration lumen 1442 serves as a conduit for removal of unwantedmaterials (e.g., excess fluids and resected tissue fragments) from thesurgical field or target site of an ablation and/or resection procedure,essentially as described hereinabove with reference to other embodimentsof an electrosurgical probe. The embodiment of FIG. 15A may furtherinclude a fluid delivery device (see, for example, FIG. 15B).

FIG. 15B shows electrosurgical probe 1400 including resection unit 1406and fluid delivery port 1430 located distal to resection unit 1406,according to one embodiment of the invention. Fluid delivery port 1430is coupled to fluid delivery tube 1434 via a fluid delivery lumen 1432.Fluid delivery lumen 1432 serves as a conduit for providing a quantityof an electrically conductive fluid to resection unit 1406 and/or thetarget site of an ablation and resection procedure. The embodiment ofFIG. 15B may further include an aspiration device (see, for example,FIG. 15A). In the embodiment of FIG. 15B, tube 1434 is coupled to probe1400 at handle 1404, however other arrangements for coupling tube 1434to probe 1400 are also within the scope of the invention.

FIGS. 16A-F each show a resection unit 1406 a-f as seen in plan view,wherein each resection unit 1406 a-f includes a resection electrodesupport 1408 and at least one resection electrode head 1412, accordingto various embodiments of the invention. Each resection electrode 1410(e.g., FIG. 13), may have a single terminal or resection electrode head1412, such that each resection electrode head 1412 is independentlycoupled to a power supply (e.g., power supply 428 of FIG. 2).Alternatively, each resection electrode 1410 may have a plurality ofterminals or resection electrode heads 1412. Each resection electrode1410 may be coupled to a power supply unit (not shown in FIGS. 16A-F)via a connection block and connector cable, essentially as describedhereinabove (e.g., with reference to FIGS. 2 & 4).

FIG. 16A indicates the longitudinal axis 1406′ of resection units 1406a-f, as well as electrode support distal end 1408 a (indication oflongitudinal axis 1406′ and support distal end 1408 a are omitted fromFIGS. 16A-F for the sake of clarity, however the orientation ofresection units 1406 b-f is the same as that of resection unit 1406 a).In each of FIGS. 16A-F, resection electrode heads 1412 are depicted ashaving an elongated, substantially rectangular shape in plan view.However, other shapes and arrangements for resection electrode heads1412 are also within the scope of the invention.

FIGS. 16A-F show just some of the arrangements of resection electrodehead(s) 1412 on each resection electrode support 1408, according tovarious embodiments. Briefly, FIG. 16A shows a single resectionelectrode head 1412 located substantially centrally within support 1408and aligned approximately perpendicular to longitudinal axis 1406′. FIG.16B shows a plurality of resection electrode heads 1412 arrangedsubstantially parallel to each other and aligned substantiallyperpendicular to axis 1406′. FIG. 16C shows a plurality of resectionelectrode heads 1412 arranged substantially parallel to each other andaligned substantially perpendicular to axis 1406′, and an additionalresection electrode head 1412 arranged substantially parallel to axis1406′. FIG. 16D shows a plurality of resection electrode heads 1412arranged substantially parallel to each other and aligned at an angleintermediate between parallel to axis 1406′ and perpendicular to axis1406′. FIG. 16E shows a plurality of resection electrode heads 1412including a first substantially parallel array 1412 a aligned at a firstangle with respect to axis 1406′ and a second substantially parallelarray 1412 b aligned at a second angle with respect to axis 1406′. FIG.16F shows a plurality of resection electrode heads 1412 having anarrangement similar to that described for FIG. 16E, wherein resectionelectrode heads 1412 are of different sizes.

FIG. 17 illustrates an angle at which a resection electrode head 1412may be arranged on electrode support 1408 with respect to thelongitudinal axis 1406′ of resection unit 1406. According to certainembodiments, resection electrode heads 1412 may be arranged on electrodesupport 1408 at an angle in the range of from 0° to about 175° withrespect to longitudinal axis 1406′. In embodiments having first andsecond parallel arrays of resection electrode heads 1412, e.g., FIG.16E, first array 1412 a is preferably arranged at an angle α in therange of from about 90° to 170°, and more preferably from about 105° to165°. Second array 1412 b is preferably arranged at an angle β in therange of from about 10° to 90°, and more preferably from about 15° to75°.

FIG. 18A shows in plan view a resection electrode support 1408 arrangedon shaft distal end portion 1402 a, wherein electrode support 1408includes resection electrode head 1412. FIGS. 18B-D each show a profileof a resection electrode head 1412 on an electrode support 1408 as seenalong the line 18B-D of FIG. 18A. From an examination of FIGS. 18B-D itcan be readily seen that, according to certain embodiments of theinvention, resection electrode head 1412 may protrude a significantdistance from the external surface of shaft 1402. Typically, eachresection electrode head 1412 protrudes from resection electrode support1408 by a distance in the range of from about 0.1 to 20 mm, andpreferably by a distance in the range of from about 0.2 to 10 mm.Resection electrode head 1412 may have a profile which is substantiallysquare or rectangular; arched or semi-circular; or angular and pointed,as represented by FIGS. 18B-D, respectively. Other profiles and shapesfor resection electrode head 1412 are also within the scope of theinvention. Only one resection electrode head 1412 is depicted perelectrode support 1408 in FIGS. 18A-D. However, according to theinvention, each electrode support 1408 may have a plurality of resectionelectrode heads 1412 arranged thereon in a variety of arrangements (see,e.g., FIGS. 16A-F).

In the embodiments of FIGS. 18B-D, each electrode head 1412 is in theform of a filament or wire of electrically conductive material. In oneembodiment, the filament or wire comprises a metal. Such a metal ispreferably a durable, corrosion resistant metal. Suitable metals forconstruction of resection electrode head 1412 include, withoutlimitation, tungsten, stainless steel alloys, platinum or its alloys,titanium or its alloys, molybdenum or its alloys, and nickel or itsalloys. In embodiments wherein each electrode head 1412 is in the formof a filament or wire, the diameter of the wire is preferably in therange of from about 0.05 mm to about 5 mm, more preferably in the rangeof from about 0.1 to about 2 mm.

FIGS. 19A-I each show a cross-section of the filament or wire ofresection electrode head 1412 as seen, for example, along the lines19A-I of FIG. 18B. Evidently, a variety of different cross-sectionalshapes for resection electrode head 1412 are possible. For example,resection electrode head 1412 may be substantially round or circular,substantially square, or substantially triangular in cross-section, asdepicted in FIGS. 19A-C, respectively. Resection electrode head 1412 mayhave a cross-section having at least one curved side. For example, head1412 d of FIG. 19D has two substantially parallel sides and two concavesides. Head 1412 e of FIG. 19E has four concave sides forming fourcusps, while head 1412 f (FIG. 19F) includes three concave sides formingthree cusps. FIGS. 19G-I each depict a cross-section of a wire orfilament having serrations on at least one side thereof. Resectionelectrode head 1412 g comprises a filament having a substantiallycircular cross-section, wherein the circumference of the filament isserrated. In another embodiment (not shown) a selected portion of thecircumference of a substantially round filament may be serrated.Resection electrode head 1412 h (FIG. 19H) comprises a filament having asubstantially square cross-section, Wherein a leading or cutting edgeportion 1413 h of the filament is serrated. FIG. 19I shows a head 1412 icomprising a filament of an electrically conductive material having asubstantially crescent-shaped or semi-circular cross-sectional shape,wherein cutting edge portion 1413 i is serrated. In addition, othercross-sectional shapes for electrode head 1412 are contemplated and arewithin the scope of the invention. Preferably, the cross-sectional shapeand other features of resection electrode head 1412 promote high currentdensities in the vicinity of resection electrode head 1412 followingapplication of a high frequency voltage to resection electrode head1412. More preferably, the cross-sectional shape and other features ofresection electrode head 1412 promote high current densities in thevicinity of a leading or cutting edge, e.g., edge 1413 h, 1413 i, ofresection electrode head 1412 following application of a high frequencyvoltage to resection electrode head 1412. As noted previously, highcurrent densities promote generation of a plasma in the presence of anelectrically conductive fluid, and the plasma in turn efficientlyablates tissue via the Coblation® procedure or mechanism. Preferably,the cross-sectional shape and other features of resection electrode head1412 are also adapted for maintenance of the plasma in the presence of astream of fluid passing over resection electrode head 1412. In oneembodiment, the cross-sectional shape and other features of resectionelectrode head 1412 are also adapted for the efficient mechanicalresection, abrading, or severing of, at least, soft tissue (such asskeletal muscle, skin, cartilage, etc.).

In one embodiment a cutting edge, e.g., edge 1413 h, 1413 i, is adaptedfor both ablating and resecting tissue. Depending on the embodiment,cutting edge 1413 h, 1413 i may be oriented, or point, in variousdirections relative to the longitudinal axis of shaft 1402. For example,depending on the particular embodiment of probe 1400, and on theparticular surgical procedure(s) for which embodiments of probe 1400 aredesigned to perform, cutting edge 1413 h, 1413 i may be orienteddistally, proximally, or laterally.

Referring now to FIG. 20, a surgical kit 1500 for resecting and/orablating tissue according to the invention will now be described. FIG.20 schematically represents surgical kit 1500 including electrosurgicalprobe 1400, a package 1502 for housing probe 1400, a surgical instrument1504, and an instructions for use 1506. Instructions for use 1506include instructions for using probe 1400 in conjunction with apparatusancillary to probe 1400, such as power supply 428 (FIG. 2). Package 1502may comprise any suitable package, such as a box, carton, etc. In anexemplary embodiment, package 1502 includes a sterile wrap or wrapping1504 for maintaining probe 1400 under aseptic conditions prior toperforming a surgical procedure.

An electrosurgical probe 1400 of kit 1500 may comprise any of theembodiments described hereinabove. For example, probe 1400 of kit 1500may include shaft 1402 having at least one resection electrode 1410 atshaft distal end 1402 a, and at least one connector (not shown)extending from the at least one resection electrode 1410 to shaftproximal end 1402 b for coupling resection electrode 1410 to a powersupply. Probe 1400 and kit 1500 are disposable after a single procedure.Probe 1400 may or may not include a return electrode 1420.

Instructions for use 1506 generally includes, without limitation,instructions for performing the steps of: adjusting a voltage level of ahigh frequency power supply to effect resection and/or ablation oftissue at the target site; connecting probe 1400 to the high frequencypower supply; positioning shaft distal end 1402 a within an electricallyconductive fluid at or near the tissue at the target site; andactivating the power supply to effect resection and/or ablation of thetissue at the target site. An appropriate voltage level of the powersupply is usually in the range of from about 40 to 400 volts RMS foroperating frequencies of about 100 to 200 kHz. Instructions 1506 mayfurther include instruction for advancing shaft 1402 towards the tissueat the target site, and for moving shaft distal end portion 1402 a inrelation to the tissue. Such movement may be performed with or withoutthe exertion of a certain mechanical force on the target tissue viaresection unit 1406, depending on parameters such as the nature of theprocedure to be performed, the type of tissue at the target site, therate at which the tissue is to be removed, and the particular design orembodiment of probe 1400/resection unit 1406.

FIGS. 21A-B schematically represent a method of performing a resectionand ablation electrosurgical procedure, according to another embodimentof the invention, wherein step 1600 (FIG. 421A) involves providing anelectrosurgical probe having a resection unit. The probe provided instep 1600 includes a shaft distal end, wherein the resection unit isdisposed at the shaft distal end, either laterally or terminally. Theresection unit includes an electrode support comprising an insulatingmaterial and at least one resection electrode head arranged on theelectrode support. Step 1602 involves adjusting a voltage level of apower supply, wherein the power supply is capable of providing a highfrequency voltage of a selected voltage level and frequency. The voltageselected is typically between about 5 kHz and 20 MHz, essentially asdescribed hereinabove. The RMS voltage will usually be in the range offrom about 5 volts to 1000 volts, and the peak-to-peak voltage will bein the range of from about 10 to 2000 volts, again as describedhereinabove. The actual or preferred voltage will depend on a number offactors, including the number and size of resection electrodescomprising the resection unit.

Step 1604 involves coupling the probe to the power supply unit. Step1606 involves advancing the resection unit towards tissue at a targetsite whence tissue is to be removed. In optional step 1608, a quantityof an electrically conductive fluid may be applied to the resection unitand/or to the target site. For performance of a resection and ablationprocedure in a dry field, optional step 1608 is typically included inthe procedure. Step 1608 may involve the application of a quantity of anelectrically conductive fluid, such as isotonic saline, to the targetsite. The quantity of an electrically conductive fluid may be controlledby the operator of the probe. The quantity of an electrically conductivefluid applied in step 1608 may be sufficient to completely immerse theresection unit and/or to completely immerse the tissue at the targetsite. Step 1610 involves applying a high frequency voltage to theresection unit via the power supply unit. Step 1612 involves contactingthe tissue at the target site with the resection unit.

With reference to FIG. 21B, optional step 1614 involves exertingpressure on the tissue at the target site by applying a force to theprobe, while the resection unit is in contact with the tissue at thetarget site, in order to effect resection of tissue. Typically, such aforce is applied manually by the operator (surgeon), although mechanicalapplication of a force to the probe, e.g., by a robotic arm undercomputer control, is also possible. The amount of any force applied inoptional step 1614 will depend on factors such as the nature of thetissue to be removed, the design or embodiment of the probe, and theamount of tissue to be resected. For example, in the absence of anymechanical force applied to the tissue, tissue removal from the targetsite is primarily or solely by ablation. On the other hand, with theelectrical power turned off, either transiently or for all or a portionof a procedure, the probe may be used for mechanical resection oftissue. Typically, however, the probe is used for the concurrentelectrical ablation and mechanical resection of tissue.

Step 1616 involves moving the resection unit of the probe with respectto the tissue at the target site. Typically, step 1616 involves movingthe resection unit and the at least one resection electrode head in adirection substantially perpendicular to a direction of any pressureexerted in step 1614, or in a direction substantially parallel to asurface of the tissue at the target site. Typically, step 1616 isperformed concurrently with one or more of steps 1608 through 1614. Inone embodiment, step 1616 involves repeatedly moving the resection unitwith respect to the tissue at the target site until an appropriatequantity of tissue has been removed from the target site. Typically, aportion of the tissue removed from the target site is in the form ofresected tissue fragments. Step 1618 involves aspirating the resectedtissue fragments from the target site via at least one aspiration porton the shaft, wherein the at least one aspiration port is coupled to anaspiration lumen. In one embodiment, the probe includes at least onedigestion electrode capable of aggressively ablating resected tissuefragments. Step 1620 involves ablating resected tissue fragments withthe at least one digestion electrode. In one embodiment, the at leastone digestion electrode is arranged within the aspiration lumen, and theresected tissue fragments are ablated within the aspiration lumen.

FIG. 22 schematically represents a method of making a resection andablation electrosurgical probe, according to the invention, wherein step1700 involves providing a shaft having a resection unit. The shaftprovided in step 1700 includes a shaft proximal end and a shaft distalend, wherein the resection unit is disposed at the shaft distal end,either laterally or terminally. In one embodiment, the shaft comprisesan electrically conductive lightweight metal cylinder. The resectionunit includes an electrode support comprising an insulating material andat least one resection electrode arranged on the electrode support. Eachresection electrode includes a resection electrode head. Each resectionelectrode head typically comprises a wire, filament, or blade of a hardor rigid, electrically conductive solid material, such as tungsten,stainless steel alloys, platinum or its alloys, titanium or its alloys,molybdenum or its alloys, nickel or its alloys, and the like.

Typically, the shaft provided in step 1700 further includes at least onedigestion electrode capable of aggressively ablating tissue fragments.In one embodiment, the at least one digestion electrode is arrangedwithin the aspiration lumen. Each digestion electrode typicallycomprises an electrically conductive metal, such as tungsten, stainlesssteel alloys, platinum or its alloys, titanium or its alloys, molybdenumor its alloys, nickel or its alloys, aluminum, gold, or copper, and thelike. Typically, the shaft provided in step 1700 further includes areturn electrode.

In one embodiment, the method includes step 1702 which involves encasinga portion of the shaft within an insulating sleeve to provide anelectrically insulated proximal portion of the shaft and an exposeddistal portion of the shaft. The exposed distal portion of the shaftdefines a return electrode of the probe. The insulating sleeve typicallycomprises a substantially cylindrical length of a flexible insulatingmaterial such as polytetrafluoroethylene, a polyimide, and the like.Such flexible insulating materials are well known in the art. In oneembodiment, the resection electrode support is disposed on the returnelectrode. The resection electrode support typically comprises anelectrically insulating material such as a glass, a ceramic, a silicone,a polyurethane, a urethane, a polyimide, silicon nitride, teflon,alumina, or the like. The electrode support serves to electricallyinsulate the at least one resection electrode head from the returnelectrode. Step 1704 involves providing a handle having a connectionblock. Step 1706 involves coupling the resection electrodes and thedigestion electrodes to the connection block. The connection blockprovides a convenient mechanism by which the resection and digestionelectrodes may be coupled to a high frequency power supply. Step 1708involves affixing the shaft proximal end to the handle.

FIGS. 23A and 23B show a side view and an end-view, respectively, of anelectrosurgical suction apparatus 2100, according to another embodimentof the invention. Apparatus 2100 generally includes a shaft 2102 havinga shaft distal end portion 2102 a and a shaft proximal end portion 2102b, the latter affixed to a handle 2104. An aspiration tube 2144, adaptedfor coupling apparatus 2100 to a vacuum source, is joined at handle2104. An electrically insulating electrode support 2108 is disposed onshaft distal end portion 2102 a. Electrode support 2108 may comprise adurable or refractory material such as a ceramic, a glass, afluoropolymer, or a silicone rubber. In one embodiment, electrodesupport 2108 comprises an alumina ceramic. A plurality of activeelectrodes 2110 are arranged on electrode support 2108.

Shaft 2102 may comprise an electrically conducting material, such asstainless steel alloys, tungsten, platinum or its alloys, titanium orits alloys, molybdenum or its alloys, and nickel or its alloys. Aninsulating sleeve 2118 covers a portion of shaft 2102. An exposedportion of shaft 2102 located between sleeve distal end 2118 a andelectrode support 2108 defines a return electrode 2116. In analternative embodiment (not shown), shaft 2102 may comprise aninsulating material and a return electrode may be provided on the shaft,for example, in the form of an annulus of an electrically conductivematerial.

FIG. 23B shows an end-view of apparatus 2100, taken along the lines23B-23B of FIG. 23A. A plurality of active electrodes 2110 are arrangedsubstantially parallel to each other on electrode support 2108. A voidwithin electrode support 2108 defines an aspiration port 2140.Typically, the plurality of active electrodes 2110 span or traverseaspiration port 2140, wherein the latter is substantially centrallylocated within electrode support 2108. Aspiration port 2140 is incommunication with an aspiration channel 2142 (FIG. 23C) for aspiratingunwanted materials from a surgical site.

FIG. 23C shows a longitudinal cross-section of the apparatus of FIG.23A. Aspiration channel 2142 is in communication at its proximal endwith aspiration tube 2144. Aspiration port 2140, aspiration channel2142, and aspiration tube 2144 provide a convenient aspiration unit orelement for removing unwanted materials, e.g., ablation by-products,excess saline, from the surgical field during a procedure. The directionof flow of an aspiration stream during use of apparatus 2100 isindicated by the solid arrows. Handle 2104 houses a connection block2105 adapted for independently coupling active electrodes 2110 andreturn electrode 2116 to a high frequency power supply (e.g., FIG. 1).An active electrode lead 2121 couples each active electrode 2110 toconnection block 2105. Return electrode 2116 is independently coupled toconnection block 2105 via a return electrode connector (not shown).Connection block 2105 thus provides a convenient mechanism forindependently coupling active electrodes 2110 and return electrode 2116to a power supply (e.g., power supply 28, FIG. 1).

FIG. 24A is a longitudinal cross-section of the shaft distal end 2102 aof an electrosurgical suction apparatus 2100, showing the arrangement ofactive electrode 2110 according to one embodiment. Active electrode 2110includes a loop portion 2113, a free end 2114, and a connected end 2115.Active electrode 2110 is disposed on electrode support 2108, and is incommunication at connected end 2115 with active electrode lead 2121 forcoupling active electrode 2110 to connection block 2105. Aspirationchannel 2142 is omitted from FIG. 24A for the sake of clarity. FIG. 24Bis a cross-section of active electrode 2110 as taken along the lines24B-24B of FIG. 24A, showing an electrode distal face 2111. AlthoughFIG. 24B shows a substantially rectangular shape for active electrode2110, other shapes (e.g., those depicted in FIGS. 19A-I) are alsopossible under the invention.

FIG. 24C shows in more detail active electrode 2110 in the form of aloop of flattened wire in communication with electrode lead 2121,according to one embodiment of the invention. Typically, free end 2114terminates within electrode support 2108 or within another electricallyinsulating material. In this embodiment, electrode lead 2121 is integralwith active electrode 2110. Electrode lead 2121 and active electrode2110 may each comprise a highly conductive, corrosion-resistant metalsuch as tungsten, stainless steel alloys, platinum or its alloys,titanium or its alloys, molybdenum or its alloys, nickel or its alloys,iridium, aluminum, gold, copper, and the like. In one embodiment, one orboth of electrode lead 2121 and active electrode 2110 may each comprisea platinum/iridium alloy, such as an alloy comprising from about 85% to95% platinum and from about 5% to 15% iridium.

FIG. 25A shows an electrosurgical suction apparatus 2100 having an outersheath 2152 external to shaft 2102 to provide an annular fluid deliverychannel 2150, according to another aspect of the invention. The distalterminus of outer sheath 2152 defines an annular fluid delivery port2156 at a location proximal to return electrode 2116. Outer sheath 2152is in communication at its proximal end with a fluid delivery tube 2154at handle 2104. Fluid delivery port 2156, fluid delivery channel 2150,and tube 2154 provide a convenient fluid delivery unit for providing anelectrically conductive fluid (e.g., isotonic saline) to the distal endof the suction apparatus or to a target site undergoing treatment. Thedirection of flow of an electrically conductive fluid during use ofapparatus 2100 is indicated by the solid arrows. An extraneouselectrically conductive fluid forms a current flow path between activeelectrodes 2110 and return electrode 2116, and can facilitate generationof a plasma in the vicinity of active electrodes 2110, as describedhereinabove. Provision of an extraneous electrically conductive fluidmay be particularly valuable in a dry field situation (e.g., insituations where there is a paucity of native electrically conductivebodily fluids, such as blood, synovial fluid, etc.). In an alternativeembodiment, an electrically conductive fluid, such as saline, may bedelivered to the distal end of suction apparatus 2100 by a separatedevice (not shown). FIG. 25B is a transverse cross-section of shaft 2102of the apparatus of FIG. 25A, and shows the relationship between outersheath 2152, shaft 2102, and fluid delivery port 2156. Aspirationchannel 2142 and electrode lead 2121 are omitted from FIGS. 25A, 25B forthe sake of clarity.

With reference to FIG. 26A there is shown in longitudinal cross-sectionthe shaft distal end 2102 a of an electrosurgical suction apparatus 2100including a baffle or trap 2146, according to another embodiment,wherein baffle 2146 is arranged transversely within shaft 2102 at thedistal end of aspiration channel 2142. In the embodiment shown, baffle2146 is recessed with respect to treatment surface 2109 to define aholding chamber 2148 within the void of electrode support 2108. As seenin the end view of FIG. 26B, baffle 2146 includes a plurality ofaspiration ports 2140′. The size, number, and arrangement of ports 2140′on baffle 2146 is at least to some extent a matter of design choice. Aplurality of active electrodes 2110 are arranged substantially parallelto each other on electrode support 2108. During a procedure involvingresection or ablation of tissue, any relatively large resected tissuefragments or other tissue debris drawn by suction to a location proximalto active electrodes 2110 may be retained by baffle 2146 within holdingchamber 2148. By relatively large resected tissue fragments is meantthose fragments too large to be readily drawn through ports 2140′ in anaspiration stream. Such tissue fragments temporarily retained by baffle2146 are conveniently positioned with respect to active electrodes 2110,and are readily digested by one or more of active electrodes 2110 by asuitable high frequency voltage applied between active electrodes 2110and return electrode 2116. As an additional advantage, becauseaspiration channel 2142 is wider than each of aspiration ports 2140′,the former is not subject to being clogged by resected tissue fragmentsor other debris. Using the configuration of FIGS. 26A, 26B onlyaspirations ports 2140′ are subject to (temporary) blockage; as pointedout above, any tissue fragments too large to pass through ports 2140′are rapidly digested by active electrodes 2110. Baffle 2146 may beconstructed from an electrically insulating material, such as variousplastics. Alternatively, baffle 2146 may comprise an electricallyconducting material such as various metals, in which case baffle 2146 istypically electrically isolated.

FIG. 27A is a longitudinal cross-section of a shaft distal end 2102 a ofa suction apparatus 2100, according to another embodiment, wherein shaftdistal end 2102 a is curved. The distal end of electrode support 2108defines a treatment surface 2109 (the latter perhaps best seen in FIG.28A). A curve in shaft distal end 2102 a may facilitate access oftreatment surface 2109 to a site targeted for electrosurgical treatment.Active electrodes 2110, which typically protrude from treatment surface2109 (e.g., FIGS. 28A, 28B), are omitted from FIG. 27A for the sake ofclarity.

FIG. 27B is a longitudinal cross-section of shaft distal end 2102 a of asuction apparatus 2100, according to another embodiment of theinvention, wherein the distal end of electrode support 2108 is beveledat an angle,

. Typically angle

is in the range of from about 15° to 60°, more typically from about 20°to 45°, and usually from about 25° to 35°. Active electrodes 2110 areomitted from FIG. 27B for the sake of clarity. A beveled treatmentsurface 2109 may facilitate access of shaft distal end portion 2102 a totissue at a target site as well as manipulation of shaft 2102 duringtreatment.

FIG. 28A shows a specific configuration of a shaft distal end 2102 a ofan electrosurgical suction apparatus 2100, according to one embodimentof the invention. The distal end of electrode support 2108 defines abeveled treatment surface 2109. A first, a second, and a third activeelectrode 2110 a,b,c extend from treatment surface 2109. Treatmentsurface 2109 includes a rounded perimeter 2107 which serves to eliminatesharp edges from electrode support 2108. The presence of roundedperimeter 2107 prevents mechanical damage to delicate or sensitivetissues during use of apparatus 2100. Electrode support 2108 encirclesaspiration port 2140.

Loop portions 2113 (e.g., FIG. 24C) of first, second, and third activeelectrodes, 2110 a, 2110 b, 2110 c, traverse or bridge aspiration port2140. First, second, and third active electrodes, 2110 a, 2110 b; 2110 care arranged substantially parallel to each other, and protrude fromtreatment surface 2109. In the case of second active electrode 2110 b,the orientation with respect to treatment surface 2109 of free end 2114,loop portion 2113, and connected end 2115 is at least substantially thesame. In contrast, in the case of first and third active electrodes 2110a, 2110 c, the orientation with respect to treatment surface 2109 ofloop portion 2113 is different from the orientation of connected end2115 and free end 2114. That is to say, the orientation of activeelectrodes 2110 a and 2110 c with respect to treatment surface 2109changes from a first direction in the region of connected end 2115 andfree end 2114, to a second direction in the region of loop portion 2113.

Furthermore, loop portions 2113 of first, second, and third activeelectrodes, 2110 a, 2110 b, 2110 c are oriented in different directions.Thus, second electrode 2110 b extends substantially in the direction ofthe longitudinal axis of shaft 2102, and distal face 2111 b is alsooriented in the direction of the longitudinal axis of shaft 2102. Firstand third electrodes 2110 a, 2110 c flank second electrode 2110 b, loopportions 2113 of first and second electrodes 2110 a, 2110 c are orientedtowards second electrode 2110 b, and distal faces 2111 a, 2111 c bothface towards second electrode 2110 b. In other words, first, second, andthird electrodes 2110 a, 2110 b, 2110 c all point in differentdirections.

Perhaps as best seen in FIG. 28B, each active electrode 2110 a-cincludes a distal face 2111 a-c. In the embodiment of FIGS. 28A, 28B,each distal face 2111 a, 2111 b, 2111 c faces, or is oriented in, adifferent direction as described with reference to FIG. 28A.Furthermore, a dashed line Lp drawn parallel to treatment surface 2109illustrates that the orthogonal distance, Do from treatment surface 2109to each distal face 2111 a,b,c is substantially the same for each ofactive electrodes 2110 a,b,c.

Electrosurgical suction apparatus 2100 described with reference to FIGS.23A through 23B can be used for the removal, resection, ablation, andcontouring of tissue during a broad range of procedures, includingprocedures described hereinabove with reference to other apparatus andsystems of the invention. Typically during such procedures, theapparatus is advanced towards the target tissue such that treatmentsurface 2109 and active electrodes 2110 are positioned so as to contact,or be in close proximity to, the target tissue. Each of the plurality ofactive electrodes includes a loop portion adapted for ablating tissuevia molecular dissociation of tissue components upon application of ahigh frequency voltage to the apparatus. In one embodiment, anelectrically conductive fluid may be delivered to the distal end of theapparatus via a fluid delivery channel to provide a convenient currentflow path between the active and return electrodes. A high frequencyvoltage is applied to the apparatus from a high frequency power supplyto ablate the tissue at the target site. Suitable values for variousvoltage parameters are presented hereinabove.

Unwanted materials, such as low molecular weight ablation by-products,excess extraneously supplied fluid, resected tissue fragments, blood,etc., are conveniently removed from the target site via the integralaspiration unit of the invention. Typically, such an aspiration unitcomprises an aspiration channel in communication with a distalaspiration port and a proximal aspiration tube, the latter coupled to asuitable vacuum source (not shown). Vacuum sources suitable for use inconjunction with apparatus and systems of the invention are well knownin the art.

In one embodiment, the apparatus may be reciprocated or otherwisemanipulated during application of the high frequency voltage, such thatloop portion 2113 including distal face 2111 of each active electrodemoves with respect to the target tissue, and the tissue in the region ofeach distal face 2111 is ablated via molecular dissociation of tissuecomponents. The apparatus is capable of effectively removing tissue in ahighly controlled manner, and is particularly useful in proceduresrequiring a smooth and/or contoured tissue surface.

FIG. 29 is a block diagram schematically representing an electrosurgicalsystem 2200, according to one embodiment of the invention. System 2200includes an electrosurgical instrument 2201, such as a probe orcatheter, including a shaft 2202 and an electrode assembly 2220. System2200 further includes a high frequency power supply 2228 coupled toelectrode assembly 2220. Typically, instrument 2201 further includes anaspiration unit 2230 and a fluid delivery unit 2240 coupled,respectively, to a vacuum source 2250 and a fluid source 2260.Aspiration unit 2230 is adapted for aspirating excess or unwantedmaterials from a working end of instrument 2201 or from a surgical siteduring a procedure. Fluid delivery unit 2240 is adapted for deliveringan electrically conductive fluid to the working end of instrument 2201,or to a surgical site, during certain procedures.

FIG. 30 is a block diagram schematically representing an electrosurgicalinstrument 2300, according to another aspect of the invention.Instrument 2300 includes an electrode assembly 2320 comprising anelectrode array 2310. In one embodiment, electrode assembly 2320 isdisposed on an electrically insulating electrode support 2308. Electrodearray 2310 includes a plurality of active electrodes 2312. Each activeelectrode 2312 is adapted for at least one of the following functions:i) localized ablation of a target tissue, ii) localized coagulation of atarget tissue, and iii) digestion of resected tissue fragments. In oneembodiment, electrode support 2308 comprises a ceramic, a glass, or asilicone rubber. According to one aspect of the invention, the electrodesupport includes a tissue treatment surface, and the plurality of activeelectrodes are arranged substantially parallel to each other on thetreatment surface (e.g., FIGS. 35 and 37). Other configurations for theelectrode assembly are also within the scope of the invention. Accordingto one aspect of the invention, the electrode support includes a recesswithin the tissue treatment surface (e.g., FIGS. 34C and 34E).

FIG. 31 is a block diagram schematically representing an activeelectrode 2412 for an electrosurgical instrument, according to anotherembodiment of the invention. Active electrode 2412 includes a firstfilament 2413 a, a second filament 2413 b, and a bridge portion 2414.Typically, bridge portion 2414 is suspended between first filament 2413a and second filament 2413 b. According to one embodiment of theinvention, the cross-sectional area of bridge portion 2414 is greaterthan that of either first filament 2413 a or second filament 2413 b. Inone embodiment, the bridge portion includes a first distal face, and asecond distal face contiguous with the first distal face to define adistal edge (e.g., FIGS. 34B-D). Typically, active electrode 2412comprises a material such as stainless steel, molybdenum, platinum,tungsten, palladium, iridium, titanium, or their alloys.

FIG. 32 schematically represents an electrosurgical instrument or probe2500 as seen in side view, according to another aspect of the invention.Electrosurgical instrument 2500 includes a shaft 2502, having a shaftdistal end 2502 a and a shaft proximal end 2502 b, and a handle 2504affixed to shaft proximal end 2502 b. Shaft 2502 includes an inner shaft2502′ and an outer shaft 2502″. A proximal portion of inner shaft 2502′is ensheathed within an electrically insulating sleeve or sheath 2503.In one embodiment, inner shaft 2502′ comprises a metal tube, and anexposed distal portion of inner shaft 2502′ defines a return electrode2518. Inner shaft 2502′ may comprise stainless steel, or the like, whilesheath 2503 may comprise a heat shrink tube. Outer shaft 2502″ maycomprise an electrically insulating material, such as variousresin-based composite materials, which may include a fibrous component.In one embodiment, outer shaft 2502″ comprises a Polygon Tube™ (PolygonCompany, Walkerton, Ind.).

Again with reference to FIG. 32, an electrically insulating electrodesupport or spacer 2508 is disposed at shaft distal end 2502 a.Typically, at least one active electrode is disposed on electrodesupport 2508. (Active electrodes are omitted from FIG. 32, e.g., for thesake of clarity.) An aspiration lumen 2534 is disposed within shaft2502. A distal end of aspiration lumen 2534 is coupled to a void inelectrode support 2508 (e.g., FIGS. 34E, 35). A proximal end ofaspiration lumen 2534 is coupled to an aspiration tube 2536. Aspirationlumen 2534 is adapted for removing unwanted materials from the workingend of instrument 2500 via an aspiration stream (represented in FIG. 32by open arrows). As shown in FIG. 32, aspiration tube 2536 extends fromhandle 2504, although other configurations are possible under theinvention. In one embodiment, the aspiration lumen may be accommodatedwithin a multi-lumen tube (not shown), wherein the multi-lumen tube lieslongitudinally within shaft 2502. In one embodiment, the multi-lumentube is formed as a plastic extrusion product, the latter well known inthe art. Aspiration tube 2536 is adapted for coupling to a suitablevacuum source. Such vacuum sources are well known to the skilledartisan.

FIG. 33A is a side view of the working or distal end 2600 a of anelectrosurgical instrument having a fluid delivery element, according toanother aspect of the invention. A shaft 2602, e.g., comprising a metaltube, includes a plurality of external, longitudinal grooves 2635. Anelectrically insulating electrode support or spacer 2608 is disposed ata shaft distal end 2602 a. Active electrodes (e.g., FIGS. 34A-D) areomitted from FIG. 33A for the sake of clarity. A portion of shaft 2602is ensheathed within an electrically insulating sleeve or sheath 2603. Alongitudinal void or fluid channel 2634 is defined jointly by eachgroove 2635 and an inner surface of sheath 2603. In one embodiment,grooves 2635 are restricted to a distal portion of the shaft. Each ofthe plurality of fluid channels 2634 may be coupled to a fluid sourcevia a fluid delivery tube (e.g., FIGS. 15B, 25A), whereby anelectrically conductive fluid, e.g., saline, may be delivered to workingend 2600 a in the vicinity of electrode support 2608. An exposed distalportion of shaft 2602 defines a return electrode 2618. Thus, grooves2635 extend along return electrode 2618, whereby fluid may be delivereddirectly to return electrode 2618. In some embodiments, the distal endof the shaft may be curved (e.g., FIGS. 24A, 34B), and each groove mayfollow the contour or curve of the shaft.

FIG. 33B is a cross-sectional view taken along the lines 23B-23B of FIG.33A showing sheath 2603 ensheathing shaft 2602, a plurality of externalgrooves 2635 on shaft 2602, and a corresponding plurality of fluidchannels 2634 between shaft 2602 and an internal surface of sheath 2603.In one embodiment, sheath 2603 comprises a heat shrink tube. AlthoughFIG. 33B shows six external grooves/fluid delivery channels 2635/2634,other numbers and arrangements are also within the scope of theinvention.

FIG. 34A is a side view of an electrosurgical instrument 2700, accordingto one embodiment of the invention. Instrument 2700 includes a shaft2702, having a shaft distal end 2702 a and a shaft proximal end 2702 b,and a handle 2704 at shaft proximal end 2702 b. A distal portion ofshaft 2702 is ensheathed within an electrically insulating sleeve orsheath 2703. In one embodiment, sheath 2703 may comprise a heat shrinktube. An exposed (non-insulated) portion of shaft distal end 2702 adefines a return electrode. In one embodiment, return electrode 2718comprises an exposed, or naked, length of a metal tube or cylinder. Inthe embodiment shown in FIG. 34A, shaft distal end 2702 a is curved.

Again with reference to FIG. 34A, an electrically insulating electrodesupport 2708 is disposed at shaft distal end 2702 a. At least one activeelectrode 2712 is disposed on electrode support 2708. FIG. 34A shows anelectrode array 2710 comprising two active electrodes 2712. However,electrode arrays having other numbers of active electrodes are alsowithin the scope of the invention. Handle 2704 houses a connection block2706. Each active electrode 2712 and return electrode 2718 are coupledto connection block 2706 via one or more electrode leads or filaments(e.g., FIG. 23C). Connection block 2706 permits the facile connection ofactive electrodes 2712 and return electrode 2718 to a high frequencypower supply (e.g., FIGS. 1, 29). In one embodiment, each activeelectrode is independently coupled to a separate channel of the highfrequency power supply.

FIG. 34B is a side view of the working or distal end of instrument 2700of FIG. 34A, showing active electrode 2712 protruding from electrodesupport 2708. Only a single active electrode is shown in FIG. 34B, forthe sake of clarity. Thus, the numbers of active electrodes shown in theDrawings should not be construed as limiting the invention. Electrodesupport 2708 includes a treatment surface 2707 and a recess 2709 withintreatment surface 2707.

FIG. 34C shows the working end of instrument 2700 as seen along thelines 34C-34C of FIG. 34B. Each active electrode 2712 includes first andsecond filaments 2713 a, 2713 b extending from treatment surface 2707 ofsupport 2708, and a bridge portion 2714 between first filament 2713 aand second filament 2713 b. Bridge portion 2714 is coupled to connectionblock 2706 (FIG. 34A) via at least one of first filament 2713 a andsecond filament 2713 b. Bridge portion 2714 is spaced from treatmentsurface 2707 by a minimum distance typically in the range of from about0.05 to 3 mm. More typically, bridge portion 2714 is spaced fromtreatment surface 2707 by a distance not less than from about 0.1 to 2mm. Bridge portion 2714 spans recess 2709. A void within recess 2709defines an aspiration port 2732. Aspiration port 2732 is incommunication proximally within an aspiration lumen 2734 within shaft2702.

FIG. 34D shows a distal portion of bridge portion 2714 of activeelectrode 2712 as seen along the lines 34D-34D of FIG. 34C. Thus, bridgeportion 2714 includes a first distal face 2715 a and a second distalface 2715 b contiguous with first distal face 2715 a to define a distaledge 2716, wherein distal edge 2716 is characterized by angle x.Typically, angle x is an acute angle in the range of from about 25° to85°. In one embodiment, angle x is in the range of from about 30° to65°. Each active electrode 2712 may have one or more other edges inaddition to distal edge 2716. While not being bound by theory, applicantbelieves that the presence of edge(s) on the active electrode(s)generates relatively high current densities and promotes formation of aplasma in the vicinity of the active electrode(s) upon application of ahigh frequency voltage between the active electrode(s) and the returnelectrode.

FIG. 34E is a perspective view of the working end of instrument 2700 ofFIG. 34A, showing the location of recess 2709 with respect to treatmentsurface 2707, as well as the location of aspiration port 2732 withinrecess 2709. In the embodiment shown in FIG. 34E, treatment surface 2707is substantially planar, recess 2709 is substantially linear and bisectstreatment surface 2707, while aspiration port 2732 is substantiallycentrally located within recess 2709. However, other configurations andlocations for these elements are also within the scope of the invention.The active electrode(s) are omitted from FIG. 34E for the sake ofclarity.

FIG. 35 is a face view of an electrode assembly 2820 of anelectrosurgical instrument, illustrating the configuration of aplurality of active electrodes on an electrode support 2808, each activeelectrode including a bridge portion, 2814 a-n. Electrode support 2808includes a treatment surface 2807 and a recess 2809. Bridge portions2814 a, 2814 b, 2814 n are arranged substantially parallel to each otheron treatment surface 2707. Each bridge portion 2814 a, 2814 b, 2814 nspans recess 2809 and is arranged substantially orthogonal thereto. Anaspiration port 2832 is located within recess 2809. In the embodimentshown in FIG. 35, bridge portion 2814 b spans aspiration port 2832.Although FIG. 35 shows three parallel active electrodes, other numbersand configurations of active electrodes are also within the scope of theinvention.

FIG. 36 is a side view of a working or distal end 2900 a of anelectrosurgical instrument, including a shaft distal end 2902 a and anelectrode support 2908 disposed at shaft distal end 2902 a. Electrodesupport 2908 includes a treatment surface 2907 arranged at an angle, ywith respect to the longitudinal axis, AX of the instrument. In oneembodiment, angle γ is in the range of from about 25° to 75°, and oftenfrom about 30° to 60°. An active electrode 2912 extends distally fromelectrode support 2908 at an angle, z with respect to treatment surface2907. In one embodiment, angle z is in the range of from about 35° to95°, and in some instances from about 60° to 85°. For the sake ofclarity, a single active electrode 2912 is schematically represented inFIG. 36 as a rectangular shape. Instruments of the invention may featureactive electrodes having various geometries, e.g., as describedhereinabove.

FIG. 37 is a perspective view of an electrode assembly 3020 for anelectrosurgical instrument, according to one embodiment of theinvention. Electrode assembly 3020 includes first, second, and thirdactive electrodes 3012, 3012′, and 3012″ arranged parallel to each otheron a treatment surface 3007 of an electrode support 3008. As shown,treatment surface 3007 is substantially planar. First, second, and thirdactive electrodes 3012, 3012′, and 3012″ each comprise a first filament3013 a, 3013 a′, and 3013 a″, respectively; a second filament 3013 b,3013 b′, and 3013 b″, respectively; and a bridge portion 3014, 3014′,and 3014″, respectively. In one embodiment, each bridge portion isarranged substantially orthogonal to both the first and secondfilaments, and each bridge portion is oriented in substantially the samedirection. Bridge portions 3014, 3014′, and 3014″, have lengthsrepresented as l₁, l₂, and l₃, respectively. As shown in FIG. 37, l₁ isapproximately the same as l₃, while l₂ is greater than l₁ and l₃. In oneembodiment, the distance between the first and second filaments of anactive electrode (e.g., electrode 3012) is less than the length of thecorresponding bridge portion. Thus, the distance 11′ between first andsecond filaments 3013 a, 3013 b is less than the length l₁ of bridgeportion 3014. Typically, each pair of filaments, e.g., first and secondfilaments 3013 a, 3013 b, extend through a corresponding pair ofelectrode ports (not shown) located within support 3008.

FIG. 38 schematically represents a series of steps involved in a methodof treating a target tissue during a surgical procedure, according toanother embodiment of the invention, wherein step 3100 involvesproviding an electrosurgical instrument or probe adapted for treatingthe target tissue. In one embodiment, an instrument provided in step3100 is adapted for the controlled ablation of the target tissue, aswell as spot coagulation of tissue, and the digestion of resected tissuefragments. Electrosurgical instruments of step 3100 may have certainelements, features, and characteristics of various embodiments of theinvention described hereinabove. In one embodiment, an instrumentprovided in step 3100 includes a distal or working end, and an electrodeassembly disposed at the working end, wherein the electrode assemblycomprises at least one active electrode disposed on an electricallyinsulating electrode support. According to one aspect of the invention,an instrument of step 3100 is adapted for the controlled removal of softtissue during laparoscopic procedures. In one embodiment, such aninstrument is adapted for the controlled removal and/or coagulation ofectopic endometrial lesions or implants. In use, instruments of theinvention are coupled to a high frequency power supply (e.g., FIG. 1)adapted for operation in the ablation mode or the sub-ablation mode. Inone embodiment, the instrument has a curved working end (e.g., FIG.34A).

Step 3102 involves advancing the working end of the instrument towards atarget tissue. In one embodiment, the instrument is advanced towards thetarget tissue via a laparoscope. In one embodiment, the instrument isadapted for advancement through a 5 mm cannula. Step 3104 involvespositioning the electrode assembly in at least close proximity to thetarget tissue, e.g., such that at least one active electrode is incontact with, or adjacent to, the target tissue. As an example, thetarget tissue may be an endometrial implant located on the bowel, theovaries, the urinary bladder, or the ureter of a patient.

Step 3106 involves applying a high frequency voltage between the activeelectrode(s) and a return electrode, in either the ablation mode or thesub-ablation mode, such that the target tissue is ablated (e.g., viaCoblation®), or coagulated (sub-ablation mode). The parameters of theapplied voltage are typically within the ranges cited hereinabove, e.g.,in the range of from about 200 volts RMS to 1000 volts RMS in theablation mode, and in the range of from about 10 volts RMS to 150 voltsRMS in the sub-ablation mode. In one embodiment, the return electrode isintegral with the probe, and comprises a non-insulated portion of ametal tube located proximal to the active electrode(s). During and/orprior to step 3106, an electrically conductive fluid, such as isotonicsaline, may be delivered to the working end of the instrument, or to thetarget tissue, via a fluid delivery element integral with theinstrument. Such fluid may provide a current flow path between theactive electrode(s) and the return electrode.

Optional step 3108 involves manipulating the instrument such that theelectrode assembly is translated with respect to the target tissue. Inone embodiment, the electrode assembly is positioned according to step3104, and thereafter the instrument is manipulated such that the activeelectrode(s) repeatedly move over the target tissue in a smooth“brushing” motion, whereby target tissue is selectively removed withlittle or no collateral damage to underlying tissue. Removal of targettissue (e.g., abnormal tissue, such as neoplasms, or ectopic endometrialtissue) according to the invention may result in the formation ofgaseous by-products and, in some instances, resected fragments of targettissue. It is generally advantageous to remove such ablation by-productsand resected tissue fragments from the surgical site. To this end, theinstrument is typically adapted for aspirating unwanted or excessmaterials, including gaseous ablation by-products, from the surgicalsite. Step 3110 involves aspirating such unwanted or excess materialsfrom the surgical site, or from the working end of the instrument; viaan aspiration unit which may be integral with the instrument. In someembodiments, the active electrode(s) are adapted for digesting tissuefragments to form smaller fragments and/or gaseous ablation by-products,thereby preventing blockage of the aspiration unit by larger tissuefragments.

Instruments of the invention may be used during a broad range oflaparoscopic procedures, including the removal or coagulation ofendometrial tissue from the bowel, ovaries, ureter, urinary bladder, orother sites of the abdominal cavity, including ablation ofendometriomas, as well as appendectomies, and the removal of fibroidtumors, and the like.

Other modifications and variations can be made to the disclosedembodiments without departing from the subject invention. For example,other numbers and arrangements of the active electrodes on the electrodesupport are possible, under the invention. In addition, certain elementsor features of various disclosed embodiments may be substituted forcorresponding or analogous elements or features of other disclosedembodiments, or may be combined with elements and features of otherdisclosed embodiments, as will be apparent to the skilled artisan.Therefore, while certain embodiments of the present invention have beendescribed in detail, by way of example and for clarity of understanding,a variety of changes, adaptations, and modifications will be obvious tothose of skill in the art. Therefore, the scope of the present inventionis limited solely by the appended claims.

1. An electrosurgical apparatus for treating tissue at a target site,comprising: a shaft having a shaft distal end and a shaft proximal end;an electrically insulating electrode support disposed at the shaftdistal end; a plurality of active electrodes arranged substantiallyparallel to each other on the electrode support, wherein the shaftcomprises an inner shaft and an outer sheath, wherein a proximal portionof the inner shaft lies within the outer sheath, and a distal portion ofthe inner shaft extends distally from the outer sheath; and wherein thedistal portion of the inner shaft is exposed and comprises a returnelectrode spaced proximal from the plurality of active electrodes. 2.The apparatus of claim 1, wherein the inner shaft comprises a metaltube.
 3. The apparatus of claim 2, wherein the metal tube comprisesstainless steel.
 4. The apparatus of claim 2, wherein the metal tube hasa curved distal end.
 5. The apparatus of claim 1, wherein the outersheath comprises an electrically insulating tube.
 6. The apparatus ofclaim 1, the outer sheath further comprising an electrically insulatingsleeve ensheathing a length of the inner shaft, wherein the inner shaftincludes at least one longitudinal, external groove.
 7. The apparatus ofclaim 1, wherein the return electrode comprises a plurality of external,longitudinal grooves.
 8. The apparatus of claim 1, further comprising afluid delivery unit, wherein the fluid delivery unit is fluidly coupledto the shaft for delivering an electrically conductive fluid to theshaft distal end.
 9. The apparatus of claim 8, wherein the fluiddelivery unit comprises a plurality of fluid delivery channels, eachfluid delivery channel defined jointly by an external groove in theinner shaft and an inner surface of the outer sheath, wherein the outersheath comprises an electrically insulating sleeve ensheathing a lengthof the inner shaft.
 10. The apparatus of claim 1, wherein each of theplurality of active electrodes comprises a first filament, a secondfilament, and a bridge portion suspended between the first filament andthe second filament.
 11. The apparatus of claim 10, wherein theelectrode support includes a substantially planar treatment surface, andwherein each bridge portion is spaced from the treatment surface by aminimum distance in the range of from about 0.05 mm to 3 mm.
 12. Theapparatus of claim 10, wherein the electrode support includes atreatment surface and a recess within the treatment surface, and eachbridge portion spans the recess.
 13. The apparatus of claim 12, whereinthe treatment surface is bisected by the recess.
 14. The apparatus ofclaim 12, further comprising an aspiration unit adapted for aspiratingexcess or unwanted materials from a working end of the apparatus or froma surgical site.
 15. The apparatus of claim 14, wherein the aspirationunit includes an aspiration port, and wherein the aspiration port lieswithin the recess.
 16. The apparatus of claim 1, wherein each of theplurality of active electrodes including a distal edge, wherein thedistal edge is characterized by an acute angle in the range of fromabout 25° to 85°.
 17. The apparatus of claim 1, wherein the electrodesupport comprises a ceramic.
 18. The apparatus of claim 1, furthercomprising a connection block adapted for coupling the plurality ofactive electrodes to a high frequency power supply, wherein each of theplurality of active electrodes comprises a bridge portion, a firstfilament, and a second filament, and wherein at least one of the firstfilament and the second filament is coupled to the connection block. 19.An electrosurgical instrument, comprising: a shaft having a shaft distalend, the shaft distal end having a plurality of longitudinal, externalgrooves; an electrode assembly disposed at the shaft distal end; and anelectrically insulating sheath external to the shaft distal end, thesheath and the plurality of grooves jointly defining a correspondingplurality of fluid delivery channels external to the shaft distal end,each of the plurality of fluid delivery channels adapted as a fluidconduit.
 20. The instrument of claim 19, wherein the electricallyinsulating sheath comprises a heat shrink tube.
 21. The instrument ofclaim 19, wherein the electrode assembly comprises an electricallyinsulating electrode support having a treatment surface, and at leastone active electrode disposed on the treatment surface.
 22. Theinstrument of claim 21, wherein each active electrode includes a distaledge, each distal edge characterized as having an acute angle.
 23. Theinstrument of claim 19, wherein the shaft distal end is curved.